MVEC’s COVID-19 vaccine FAQs have been designed to address common queries relating to COVID-19 vaccine allergies, safety & side effects.

Please also see the MVEC COVID-19 vaccine FAQs: vaccine development, rollout, effectiveness & storage for questions specific to other vaccine topics.

For ease of reference, information has been categorised as per the below themes:

This page will be updated on a regular basis as further information becomes available regarding COVID-19 vaccines.

For questions that have not been addressed on this page or our dedicated COVID-19 resource page, please email info.mvec@mcri.edu.au for further clarification.

Administration

  • Can COVID-19 vaccines be co-administered with other vaccines?

    The Australian Technical Advisory Group on Immunisation (ATAGI) recommends a minimum interval of 7 days between administration of a COVID-19 vaccine and other vaccines.

    Shorter interval (eg. less than 7 days or co-administration on the same day) are acceptable in the following instances:

    • An increased risk of COVID-19 or another vaccine preventable disease (eg. COVID-19 outbreak, influenza outbreak, a tetanus-prone wound)
    • Logistical issues such as difficulty scheduling visits to maintain the 7 day interval

    For more information please refer to COVID-19 vaccination- ATAGI clinical guidance on COVID-19 vaccine in Australia in 2021.

  • Can COVID-19 vaccines be used interchangeably (eg. using a different vaccine brand for the first and second dose)?

    Combined or mixed COVID-19 vaccine schedules are currently not recommended in Australia. More information relating to safety and efficacy, as well as information on appropriate intervals between doses is required, with clinical trials currently underway.

    For more information please refer to MVEC: COVID-19 mixed vaccine schedules or COVID-19 vaccination- ATAGI clinical guidance on COVID-19 vaccine in Australia in 2021.

  • Can the COVID-19 vaccine be given to people who have previously or currently have COVID-19 disease (or evidence of SARS-CoV-2 infection)?

    Yes, people with previous COVID-19 disease should still be vaccinated to ensure ongoing protection. However, vaccination should be deferred until the person has fully recovered from the acute COVID-19 illness. Clinical trials indicate that it is safe to give COVID-19 vaccines in people with evidence of prior SARS-CoV-2 infection.

  • How many doses will be required? How long will I be protected and do I need a booster dose?

    The recommended schedule for Comirnaty™ is two doses given 21 days apart.

    The recommended schedule for COVID-19 AstraZeneca is two doses given 12 weeks apart (with a minimum interval of 4 weeks apart accepted in certain circumstances).

    Data regarding the length of protection following vaccination is still being gathered from phase III clinical trials. The length of protection is still unclear and hence the timing and need for a booster has not been established. Currently, no additional doses beyond the first two are recommended at this time.

  • What are the ABSOLUTE minimum and maximum intervals for each COVID-19 vaccine dose?

    Vaccination with COVID-19 AstraZeneca requires a 2-dose course, with ATAGI recommending an interval of 12 weeks between doses. In certain circumstances (eg. impending chemotherapy, amount of circulating disease etc) an absolute minimum interval of 28 days is acceptable. If the second dose is inadvertently administered with an interval of less than 28 days, repeat doses are not currently recommended. If more than 12 weeks has elapsed, the second dose should be administered as soon as possible with no need to re-start the course again. In clinical trials dose 2 was administered at a range of timepoints (4-26 weeks after the first dose) with the greatest efficacy induced when dose 2 was administered 12 weeks after the first dose.

    Vaccination with Comirnaty™ requires a 2-dose course administered 21 days apart. The absolute minimum interval is 19 days and the recommended maximum interval is 6 weeks. If the second dose is inadvertently administered with an interval of less than 19 days, repeat doses are not currently recommended. If more than 6 weeks has elapsed, the second dose should be administered as soon as possible with no need to re-start the course again. Clinical trials for Comirnaty™ assessed efficacy when doses were administered at a range of timepoints with these recommendations reflective of the best results obtained.

  • What happens if the second COVID-19 vaccine dose is given early, late or is missed?

    The recommended interval between two doses of Comirnaty™ is 21 days, with a minimum interval of 19 days and a maximum interval of 6 weeks. There is currently no recommendation for repeat doses/recommencing the course if there are variations to this advice.

    The recommended interval between two doses of COVID-19 AstraZeneca is 12 weeks, with a minimum interval of 4 weeks apart accepted in certain circumstances. There is currently no recommendation for repeat doses/recommencing the course if there are variations to this advice.

    For more information on dosing recommendations please refer to COVID-19 vaccination- ATAGI clinical guidance on COVID-19 vaccine in Australia in 2021.

  • How long will it take to develop immunity once vaccinated?

    There is some evidence that one dose of Comirnaty™ will provide partial protection after 12 days however this is likely to be short lived. Generally the time required following vaccination for the body to develop immunity will depend on the vaccine; this usually takes a number of weeks. Completing both doses of the 2 dose course is recommended.

  • Are booster doses of COVID-19 vaccines required? Will the current vaccines protect against new strain variants?

    There is currently no recommendation for booster doses of COVID-19 vaccines in Australia. However, due to the limited data on duration of protection and the emergence of SARS-CoV-2 strain mutations, international advisory committees are considering the possibility that doses with updated vaccines will be required in the future.

    To read more refer to the links below:

  • I have had a recent blood transfusion; can I have a COVID-19 vaccine?

    Recommendations following blood transfusion generally apply to live-attenuated vaccines, such as MMR (measles-mumps-rubella) or varicella vaccines. There are currently no live-attenuated COVID-19 vaccines planned for use in Australia. Comirnaty™ is an mRNA vaccine and COVID-19 AstraZeneca is a non-replicating viral vector vaccine.

    For more information please refer to the CDC: COVID-19 Vaccine FAQs for Healthcare Professionals and MVEC: Live-attenuated vaccines and immunoglobulins or blood products.

  • I have had a recent live vaccine; can I have a COVID-19 vaccine?

    ATAGI currently recommends a 7 day interval between the administration of COVID-19 vaccines and any other vaccine (including live-attenuated vaccines). Please refer to COVID-19 vaccination- ATAGI clinical guidance on COVID-19 vaccine in Australia in 2021 for more information.

  • When administering a COVID-19 vaccine the syringe disconnected from the needle and I am not sure how much of the dose my patient received, what should I do?

    If the process of administering a vaccine is interrupted and most of the dose has not been given, repeat the whole dose as soon as practicable. Please contact your safety service if there are any concerns/questions.

    To read more please refer to the Australian Immunisation Handbook: Administration of vaccines.

  • Can COVID-19 vaccines be given subcutaneously?

    Both COVID-19 AstraZeneca and Comirnaty™ should be administered via intramuscular injection. There is no safety or efficacy data relating to subcutaneous administration.

  • My patient has a history of a bleeding disorder, what is the recommendation regarding intramuscular administration of COVID-19 vaccines?

    People who are taking anticoagulant therapy or have a history of a bleeding disorder are at higher risk of haematoma formation following intramuscular injection. Prior to vaccine administration, patients should be advised of this risk.

    The correct needle size and length should be used and firm pressure should be applied to the site (no rubbing) for at least 2 minutes following immunisation.

    Subcutaneous administration is not recommended due to a lack of safety and efficacy data regarding this route of administration.

    For further information please refer to the Australian Immunisation Handbook.

  • Can women with a history of breast cancer receive COVID-19 vaccines?

    Yes. Having a history of breast cancer is not a contraindication for COVID-19 vaccination.

    ATAGI recommends COVID-19 vaccination for all immunosuppressed people (including those undergoing treatment for cancers) due to an increased risk of developing severe disease if infected with SARS-CoV-2. It is anticipated that the immune response to vaccination may be reduced in this patient group depending on the level of immune suppression.

    Lymphadenopathy has been reported as a side effect following vaccination. Given that changes in size and consistency of lymph nodes can also indicate a spread of breast cancer, the Society of Breast Imaging (SBI) has recommended breast screening take place either prior to COVID-19 vaccination or 4-6 weeks following the second dose of COVID-19 vaccines to avoid anxiety and unnecessary examination and diagnostic testing.

    To read more refer to the links below:

  • What is the recommended site for injection for patients who have had axillary lymph nodes removed/have a history of lymphoedema?

    There is no strong evidence to suggest that vaccine administration into the deltoid will increase the likelihood of lymphoedema in patients who have had lymph nodes removed or have a previous history of lymphoedema.

    Vaccine administration into the deltoid of the unaffected arm may be preferred, alternatively intramuscular injection into the vastus lateralis (thigh) can be considered.

    To read more refer to the links below:

  • My patient has a history of Guillain Barre Syndrome (GBS), is it safe to administer COVID-19 vaccines?

    Having a history of GBS is not a contraindication to vaccination with COVID-19 vaccines and as such it is safe to administer COVID-19 vaccines in this patient group.

    For more information please refer to MVEC: Guillain-Barre Syndrome page and CDC: Vaccine Considerations for People with Underlying Medical Conditions.

  • Are there any concerns regarding COVID-19 vaccines and Bell’s Palsy?

    People who have previously been diagnosed with Bell’s Palsy can receive COVID-19 vaccines. Cases of Bell’s Palsy following immunisation have been identified in participants in mRNA COVID-19 vaccine candidate clinical trials. However, as the rate of occurrence was not above the background rate expected in the general population, they are not considered to be caused by vaccination.

    For more information refer to CDC: Vaccine Considerations for People with Underlying Medical Conditions.

  • Is it safe for people with a diagnosis of Multiple Sclerosis (MS) to be immunised against COVID-19 vaccines?

    Yes. Whilst there is minimal data on the safety and efficacy of COVID-19 vaccination in people with MS, there are no theoretical concerns relating to administration in this patient group.

    For more information please refer to:

  • Can patients who are taking monoamine oxidase inhibitors (MAOI’s) be safely immunised with COVID-19 vaccines given that they should generally avoid adrenaline? What would be the appropriate treatment if they experienced anaphylaxis?

    Yes, COVID-19 vaccines should be offered to this patient group.

    True vaccine allergy, or anaphylaxis, is an extremely rare adverse event following immunisation occurring in less than 1 case per million doses administered. Post-licensure surveillance of COVID-19 vaccines show anaphylaxis following administration of COVID-19 AstraZeneca occurring at similar rates to routine vaccines [refer to TGA: AstraZeneca ChAdOx1-S COVID-19 vaccine]. Anaphylaxis following Comirnaty™, whilst still extremely rare, occurs at a slightly higher rate of approximately 4.7 cases per million doses.

    Patients who take MAOI’s have a theoretical increased risk of developing hypertensive crisis if administered adrenaline (or other specific medications/foods) due to a potential for drug interaction. In the setting of anaphylaxis, resuscitation with adrenaline remains the most appropriate treatment regardless of medical history. The benefits of treating anaphylaxis effectively far outweighs any potential risk of hypertensive crisis.

    Ensuring the diagnosis of anaphylaxis is accurate is an important step to avoid unnecessary administration of adrenaline when not clinically indicated.

    For more information refer to:

Safety

  • How can a COVID-19 vaccine be safe when it was made so quickly?

    COVID-19 vaccine development is happening “faster than usual” because of the global impact of the pandemic and the urgent need for a vaccine(s). Vaccines have traditionally been developed in consecutive sequential stages – with preclinical trials followed by phases I, II and III, often with large gaps of time in-between phases awaiting funding or manufacturing scaleup. With COVID-19, this process has been made more efficient by running one phase while simultaneously also preparing and/or recruiting for the next phase.

    It is important to note that COVID-19 vaccine candidates must pass through the exact same rigor and phases of clinical trials and do not miss any important safety and quality checks or steps. Approval is only given if the vaccine meets the appropriate requirements for safety and efficacy.

    Refer to MVEC: Vaccine development and safety, including “The Road to a COVID-19 Vaccine” animation for more information.

  • How can we be sure that the manufacturing process is safe?

    Like any medication in development, vaccine candidates must undergo rigorous testing procedures and scientific evaluation to prove not only their effect on the targeted disease, but also to determine their safety – before being licensed and registered for use in vaccination programs.

    In all three clinical trial phases, safety is continually assessed as data is gathered and a vaccine must pass all these phases before it can be considered for registration for use by the TGA. By the time a vaccine is registered, safety would have been assessed in tens of thousands of clinical trial participants and this safety data would have been rigorously evaluated by the TGA and other international drug regulatory bodies.

    The quality, sterility, potency and purity of each vaccine batch is also assessed by the TGA prior to being supplied to Australia, as is the quality of selected batches after they have been supplied.

    Once a vaccine is approved, it continues to be tested in a process known as post-licensure surveillance.

  • What are the expected side effects of a COVID-19 vaccine?

    You may experience minor side effects following COVID-19 vaccination. Common side effects include pain, redness and swelling at the injection site as well as more general side effects such as fever, chills, headache and tiredness.

    Most systemic (general) symptoms are mild to moderate in severity, occur within the first three days of vaccination, and resolve within 1–3 days of onset. These symptoms may be more common and severe following the second dose and among younger people compared to older people.

    Serious reactions like allergic reactions are extremely rare. If you have any concerns about the vaccine, ask your doctor, nurse or health care professional.

    For more information, please refer to the following documents:

  • Can a COVID-19 vaccine be given in pregnancy? When breastfeeding?

    Due to an increased risk of severe outcomes for pregnant women and their unborn babies, it is recommended that pregnant women are routinely offered Comirnaty™ at any stage of pregnancy.

    Whilst pregnant women were not included in the initial clinical trials, surveillance of international data on mRNA COVID-19 vaccine administration in pregnant women, has shown no significant safety concerns for either the mother or the baby. Further to this, antibodies have been detected in the cord blood and breastmilk of vaccinated women, suggesting a transfer of protection to the baby.

    Women who are planning pregnancy or are breastfeeding can also be vaccinated without the need for delaying a pregnancy or pausing breastfeeding.

    For more information please refer to:

  • I have received 1 dose of COVID-19 but have now discovered I am pregnant. What does that mean for completing the course?

    Vaccination with an mRNA COVID-19 vaccine should be routinely offered to pregnant women during any stage of pregnancy. This includes completing a course which was commenced prior to conception. Pregnant women and their unborn babies are at an increased risk of severe outcomes following a COVID-19 infection.

    For more information refer to the following:

  • Can a COVID-19 vaccine be given to those with immunosuppression?

    ATAGI recommends COVID-19 vaccination for all immunosuppressed people due to an increased risk of developing severe disease if infected with SARS-CoV-2. Due to limitations in clinical trials there is currently minimal data on the safety and efficacy of COVID-19 vaccination in this group, however in principle there are no theoretical risks.

    It is anticipated that the immune response to vaccination may be reduced in this patient group depending on the level of immune suppression. Hence, when vaccinating immunocompromised people, they should also be counselled about this reduced efficacy and the need to continue other prevention measures such as social distancing and mask wearing.

    Household contacts of people with immunosuppression are recommended to receive COVID-19 vaccines. This helps protect people who are immunocompromised, whether they are a child or an adult, by reducing their exposure to disease.

    Please speak to your doctor to discuss individual cases and see the following links for more information:

  • How are vaccines monitored for safety post licensure? What is the role of SAEFVIC/TGA?

    Post licensure vaccine safety monitoring in Australia occurs using a variety of mechanisms. These may include:

    SAEFVIC is the central reporting service in Victoria for any significant AEFI. SAEFVIC collects, analyses and reports data about significant AEFI as part of monitoring vaccine safety in Victoria. All reports are sent to the Therapeutic Goods Administration (TGA) who is responsible for assessing the safety of vaccines and other medicines for use in Australia.

    The role of the TGA is also to determine whether a COVID-19 vaccine candidate meets the strict safety and efficacy requirements for registration before it can be used in Australia.

    For more information refer to the Therapeutic Goods Administration: COVID-19 vaccines.

  • I think I am experiencing some side effects, should I report?

    You do not need to routinely report minor, common or expected side effects of vaccines. You should report:

    • Any event felt to be significant following immunisation, regardless of whether you think the side effect was related to the vaccine or not
    • Any expected symptoms that have not gone away after a few days
    • Any side effects following an immunisation which requires assessment by a doctor or nurse
    • Suspected shoulder injury related to vaccine administration (SIRVA)

    Reporting adverse events is not mandatory in Victoria. However doing so assist in the early investigation and identification of potential vaccine or system problems. This helps to ensure a safe and effective immunisation program, and, importantly, it maintains community confidence in vaccines.

    For more information, including how to report, please refer to MVEC: SAEFVIC.

  • I experienced side effects from the first dose of the vaccine, should I not have the second dose?

    Most side effects reported following COVID-19 vaccination are minor and usually resolve within 24-48 hours. They are not a contraindication to receiving further doses of the vaccine.

    If you have experienced any unanticipated side effects following the first dose COVID-19 vaccine, speak to your healthcare professional about the safety of a second dose.

    Any serious adverse event following vaccination should be reported to SAEFVIC and a specialist immunisation consultation may be indicated to discuss recommendations for future doses.

  • What is vaccine-associated enhanced disease?

    Vaccine-associated enhanced disease occurs when a more severe presentation of disease develops in an individual who has previously been immunised, compared with when an infection occurs without prior vaccination.

    For more information on VAED please review our reference page MVEC: Vaccine-associated enhanced disease

  • My patient has a history of Guillain Barre Syndrome (GBS), is it safe to administer COVID-19 vaccines?

    Having a history of GBS is not a contraindication to vaccination with COVID-19 vaccines and as such it is safe to administer COVID-19 vaccines in this patient group.

    For more information please refer to MVEC: Guillain-Barre Syndrome page and CDC: Vaccine Considerations for People with Underlying Medical Conditions.

  • Are there any concerns regarding COVID-19 vaccines and Bell’s Palsy?

    People who have previously been diagnosed with Bell’s Palsy can receive COVID-19 vaccines. Cases of Bell’s Palsy following immunisation have been identified in participants in mRNA COVID-19 vaccine candidate clinical trials. However, as the rate of occurrence was not above the background rate expected in the general population, they are not considered to be caused by vaccination.

    For more information refer to CDC: Vaccine Considerations for People with Underlying Medical Conditions.

  • Is it safe for people with a diagnosis of Multiple Sclerosis (MS) to be immunised against COVID-19 vaccines?

    Yes. Whilst there is minimal data on the safety and efficacy of COVID-19 vaccination in people with MS, there are no theoretical concerns relating to administration in this patient group.

    For more information please refer to:

  • Can patients who are taking monoamine oxidase inhibitors (MAOI’s) be safely immunised with COVID-19 vaccines given that they should generally avoid adrenaline? What would be the appropriate treatment if they experienced anaphylaxis?

    Yes, COVID-19 vaccines should be offered to this patient group.

    True vaccine allergy, or anaphylaxis, is an extremely rare adverse event following immunisation occurring in less than 1 case per million doses administered. Post-licensure surveillance of COVID-19 vaccines show anaphylaxis following administration of COVID-19 AstraZeneca occurring at similar rates to routine vaccines [refer to TGA: AstraZeneca ChAdOx1-S COVID-19 vaccine]. Anaphylaxis following Comirnaty™ (Pfizer/BioNTech), whilst still extremely rare, occurs at a slightly higher rate of approximately 4.7 cases per million doses.

    Patients who take MAOI’s have a theoretical increased risk of developing hypertensive crisis if administered adrenaline (or other specific medications/foods) due to a potential for drug interaction. In the setting of anaphylaxis, resuscitation with adrenaline remains the most appropriate treatment regardless of medical history. The benefits of treating anaphylaxis effectively far outweighs any potential risk of hypertensive crisis.

    Ensuring the diagnosis of anaphylaxis is accurate is an important step to avoid unnecessary administration of adrenaline when not clinically indicated.

    For more information refer to:

Allergies

  • Is it safe to administer COVID-19 vaccines to people with latex allergies?

    The COVID-19 vaccines with provisional registration for use within Australia (Comirnaty™ and COVID-19 AstraZeneca) can both be administered to people with latex allergies following standard precautions, with a 15 minute post-vaccination observation period. Neither Comirnaty™ or COVID-19 AstraZeneca vials contain latex.

    For more information please refer to the ASCIA: Allergy, Immunodeficiency, Autoimmunity and COVID-19 Vaccination Position Statement.

  • My patient has a history of allergies, is it safe to administer a COVID-19 vaccine to them?

    For patients with a history of anaphylaxis to food, drugs, venom or latex, COVID-19 vaccines can be administered in a community setting with a routine observation period of 15 minutes following vaccination.

    Individuals who have experienced the following should be referred to VicSIS for a specialist immunisation consultation prior to vaccination:

    • Immediate (within 2 hours) and generalised symptoms of an allergic reaction following receipt of a COVID-19 vaccine
    • Anaphylaxis or generalised allergic reaction to any component of a COVID-19 vaccine (eg. PEG or polysorbate 80)
    • Have a history of a systemic mast cell activation disorder with a raised tryptase who have been unable to tolerate previous intramuscular injections due to recurrent anaphylaxis
  • My patient has a history of allergy to Polyethylene Glycol (PEG), can I administer a COVID-19 vaccine to them?

    PEG is an ingredient contained in Comirnaty™. It is also a commonly used ingredient of other medications, hand sanitisers, cosmetics, bathroom products and colonoscopy preparation products, routinely used within Australia. Whilst it is uncertain whether PEG contained in mRNA vaccines may trigger anaphylaxis, additional precautions are required.

    If your patient has a history of confirmed or suspected allergy to PEG it is recommended that they are referred to an immunology/allergy/vaccination specialist for advice regarding the safety of administering an mRNA COVID-19 vaccine.

    NB: Vaccination with the Comirnaty™ COVID-19 vaccine is contraindicated in people with documented anaphylaxis to PEG.

    To read more refer to COVID-19 vaccination – ATAGI clinical guidance on COVID-19 Vaccine in Australia in 2021.

  • My patient has a history of allergy to Polysorbate 80, can I administer a COVID-19 vaccine to them?

    Polysorbate 80 is chemically related to Polyethylene Glycol (see question above) and is an ingredient in COVID-19 AstraZeneca.

    If your patient has a history of confirmed or suspected allergy to Polysorbate 80 it is recommended that they are referred to an immunology/allergy/vaccination specialist for advice regarding the safety of administering COVID-19 AstraZeneca.

    NB: Vaccination with the COVID-19 AstraZeneca is contraindicated in people with documented anaphylaxis to Polysorbate 80.

    For further information please refer to ASCIA: Allergy, Immunodeficiency, Autoimmunity and COVID-19 Vaccination Position Statement and COVID-19 vaccination – ATAGI clinical guidance on COVID-19 Vaccine in Australia in 2021.

  • Do COVID-19 vaccines contain gelatin?

    Both COVID-19 AstraZeneca and Comirnaty™ are gelatin free and safe to administer to patients who are allergic to gelatin. A standard 15-minute observation period following immunisation is recommended.

  • What are the ingredients of COVID-19 vaccines?

    There are currently 2 COVID-19 vaccine with provisional registration in use in Australia.

    Each dose of Comirnaty™ contains:

    • 30 mcg mRNA encoding the SARS-CoV-2 spike glycoprotein
    • (4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2- hexyldecanoate) (ALC-0315)
    • 2-[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide (ALC0159)
    • Distearoylphosphatidylcholine (DSPC)
    • Cholesterol
    • Potassium chloride
    • Monobasic potassium phosphate
    • Sodium chloride
    • Dibasic sodium phosphate dihydrate
    • Sucrose
    • Water for injections

    Each dose of COVID-19 AstraZeneca contains:

    • 5×1010 viral particles of ChAdOx1-S
    • Histidine
    • Histidine hydrochloride monohydrate
    • Sodium chloride
    • Magnesium chloride hexahydrate
    • Disodium edetate (EDTA)
    • Sucrose
    • Ethanol absolute
    • Polysorbate 80
    • Water for injection

    Further information can be found in the Product Information for each vaccine:

  • Is there an increased risk of anaphylaxis following COVID-19 vaccines?

    A true vaccine allergy (anaphylaxis), where a person is contraindicated from being immunised with the same vaccine in the future, is rare (in most studies reported as less than 1 case per million doses).

    Post-licensure surveillance of COVID-19 vaccines show anaphylaxis following administration of COVID-19 AstraZeneca occurring at similar rates to routine vaccines. Anaphylaxis following Comirnaty™, while still extremely rare, occurs at a slightly higher rate of approximately 4.7 cases per million doses.

    To read more follow the links below:

COVID-19 Astra-Zeneca

  • What is thrombosis with thrombocytopenia syndrome (TTS)?

    Thrombosis with thrombocytopenia syndrome (TTS), is a rare and new syndrome which has been reported in people who have received an adenoviral vector COVID-19 vaccine (eg. Johnson & Johnson/Janssen and COVID-19 AstraZeneca).

    The syndrome is distinct from other clotting conditions as it is characterised by thrombosis formation (blood clots) combined with thrombocytopenia (low platelet levels).  Symptoms occur 4-30 days following vaccination. Early recognition can lead to effective treatment.

    For more information please refer to:

  • What is the difference between Tier 1 and Tier 2 thrombosis with thrombocytopenia syndrome (TTS)?

    Tier 1 and Tier 2 definitions have been applied to TTS by the CDC (Centers for Disease Control and Prevention) in the United States. The tiers are defined by the following:

    Tier 1:

    • unusual site of thrombosis (e.g neurological – central venous sinus thrombosis [CVST] or gut – eg splanchnic vein, associated with bowel ischaemia and surgery, portal vein or other rare venous and arterial thromboses)
    • Platelet count <150,000 per microliter
    • Positive (+) heparin-P4 ELISA HIT antibody result is supportive, but not required

    Tier 2:

    • Usual sites of thrombosis such as leg or lungs (e.g. venous thromboembolism, deep vein thrombosis, pulmonary embolism)
    • Platelet count <150,000 per microliter
    • Positive (+) heparin-P4 ELISA HIT antibody result is required

    Tier 1 is more severe, with higher morbidity and mortality than Tier 2. Evidence is emerging that Tier 1 is more common in younger age groups, hence the preferential recommendation for alternative vaccines (in Australia, COVID-19 AstraZeneca is not the preferred vaccine for people aged < 50 years – see the Joint statement from ATAGI and THANZ on Thrombosis with Thrombocytopenia Syndrome (TTS) and the use of COVID-19 Vaccine AstraZeneca for further information).

  • Are there any risk factors for developing thrombosis with thrombocytopenia syndrome (TTS)? eg. age, gender etc

    There have been no known markers identified that either increase or decrease an individual’s risk of developing TTS. This includes having a past history of clots in the leg (DVT), lungs (pulmonary embolus) or heart (myocardial infarction).

    Evidence thus far indicates there is a higher risk of TTS in the younger population (< 50 years of age), although there has been a small number of cases identified in older adults. There is some evidence to suggest that the incidence is higher in women compared to men, although this may be because more vaccine doses have been administered to women in vaccine rollouts worldwide, especially those targeting healthcare professionals.

  • When do symptoms of thrombosis with thrombocytopenia syndrome (TTS) occur?

    Symptoms of TTS have been reported to occur in the 4-30 day time period following administration of a COVID-19 adenoviral vector vaccine (eg. Johnson & Johnson/Janssen or COVID-19 AstraZeneca). Current information suggests that the risk of TTS is much lower following receipt of a second dose.

    Symptoms can include

    • Cerebral venous sinus thrombosis (CVST): persistent headaches (unresponsive to simple analgesia), visual changes, focal neurological symptoms (e.g. movement or sensation changes), seizures, coma, secondary intra-cerebral haemorrhage, confusion, encephalopathy
    • Splanchnic vein thrombosis: abdominal pain
    • Pulmonary embolus: chest pain/significant respiratory symptoms or distress, dyspnoea
    • Deep vein thrombosis: leg pain, redness or swelling
    • Arterial ischaemia: pallor and coldness in limb, myocardial ischaemia
    • Thrombocytopenia: acute onset bruising or bleeding, petechial rash

    NB: These symptoms are different from the common or expected side effects following vaccination which usually occur in the first 24-48 hours and last 1-2 days.

  • Are people > 60 years of age receiving an “inferior” vaccine?

    Both Comirnaty™ and COVID-19 AstraZeneca are effective vaccines which protect against severe COVID-19 disease and hospitalisation.

    The recommendation by ATAGI does not mean or indicate that there are questions over the effectiveness of the vaccine in any age group.

  • I am under 60 years of age and have had dose 1 of the AstraZeneca vaccine, is it safe to receive dose 2?

    People who have received their first dose of COVID-19 AstraZeneca without any serious adverse events can receive their second dose. This should be done in the recommended time frame of 4-12 weeks between doses. Current information suggests that thrombosis with thrombocytopenia syndrome is more frequently reported following receipt of dose 1 of COVID-19 AstraZeneca.

    For more information refer to ATAGI statement on revised recommendations on the use of COVID-19 Vaccine AstraZeneca.

  • I am under 60 years of age and received COVID-19 AstraZeneca as my first dose, should I/can I have Comirnaty™ as my dose 2 of a COVID-19 vaccine? Or now commence a course of 2 doses of Comirnaty™ and no further doses of AstraZeneca?

    Combined or mixed COVID-19 vaccine schedules are currently not recommended in Australia. More information relating to safety and efficacy, as well as information on appropriate intervals between doses is required. Clinical trials of mixed vaccine schedules are currently underway. Current information suggests that thrombosis with thrombocytopenia syndrome (TTS) is more frequently reported following receipt of dose 1 of COVID-19 AstraZeneca. If a person has received the first dose of COVID-19 AstraZeneca without any serious adverse events such as TTS or anaphylaxis, then they can receive the second dose.

    COVID-19 vaccination is not mandatory, however immunisation is strongly recommended for all who are eligible to receive it. It is important to discuss any queries or concerns with an immunisation provider or your treating health care professional.

  • I am over 60 years of age and have a history of deep vein thrombosis (DVT’s). Is it safe for me to receive COVID-19 AstraZeneca?

    There is currently no evidence to suggest that having a history of DVT’s or other general thromboembolic disorders predisposes you to developing thrombosis with thrombocytopenia syndrome (TTS) following receipt of an adenoviral vector vaccine such as COVID-19 AstraZeneca. In contrast, there is strong evidence that COVID-19 disease is thrombogenic (promotes clot development) and may cause a variety of thromboembolic events. TTS is a unique condition involving the development of thromboses (blood clots) combined with thrombocytopenia (low platelets).

    Individuals with a history of DVT’s are encouraged to receive a COVID-19 vaccine when offered.

    Refer to the Joint statement from ATAGI and THANZ on Thrombosis with Thrombocytopenia Syndrome (TTS) and the use of COVID-19 Vaccine AstraZeneca for more information.

  • I am under 60 years of age and travelling to an area experiencing a current COVID-19 outbreak. Should I have the AstraZeneca vaccine as I am unable to source an alternative?

    ATAGI recommends that COVID-19 AstraZeneca can be administered in adults aged under 60 years of age where the benefits of protection are likely to outweigh the risks of vaccination for that individual. It is important to discuss your individual circumstances with a health care provider in order to make an informed decision. There may be some differences to this advice depending on the state/jurisdiction you live in, so please check with your local Department of Health.

    To read more refer to ATAGI statement on revised recommendations on the use of COVID-19 Vaccine AstraZeneca.

  • I am under 60 years of age and allergic to Polyethylene Glycol (PEG) which is an ingredient of Comirnaty™. Can I/should I receive COVID-19 AstraZeneca?

    PEG is an ingredient contained in Comirnaty™ and it is therefore recommended that you are referred to an immunology/allergy/vaccination specialist for immunisation advice.

    NB: Vaccination with Comirnaty™ is contraindicated in people with documented anaphylaxis to PEG.

    For more information refer to MVEC: COVID-19 vaccines and allergy or COVID-19 vaccination – ATAGI clinical guidance on COVID-19 vaccine in Australia in 2021

  • I am over 60 years of age and allergic to Polysorbate 80, an ingredient of COVID-19 AstraZeneca. Will I be able to have Comirnaty™?

    Polysorbate 80 is an ingredient contained in COVID-19 AstraZeneca and it is therefore recommended that you are referred to an immunology/allergy/vaccination specialist for immunisation advice.

    NB: Vaccination with the COVID-19 AstraZeneca is contraindicated in people with documented anaphylaxis to Polysorbate 80.

    For more information refer to MVEC: COVID-19 vaccines and allergy or COVID-19 vaccination – ATAGI clinical guidance on COVID-19 vaccine in Australia in 2021

  • I am taking hormone replacement therapy. Am I at an increased risk of thrombosis with thrombocytopenia syndrome (TTS) if I am given COVID-19 AstraZeneca?

    There is currently no evidence to suggest that taking certain medications or being prone to developing blood clots puts you at increased risk of developing TTS following receipt of COVID-19 AstraZeneca. In contrast, there is strong evidence that COVID-19 disease is thrombogenic (promotes clot development) and may cause a variety of thromboembolic events. TTS is a unique condition involving the development of thromboses (blood clots) combined with thrombocytopenia (low platelets).

    Individuals who are taking hormone replacement therapy are encouraged to receive a COVID-19 vaccine when it is offered.

    For more information please refer to: Joint statement from ATAGI and THANZ on Thrombosis with Thrombocytopenia Syndrome (TTS) and the use of COVID-19 Vaccine AstraZeneca.

  • I am over 60 years of age and have a history of atrial fibrillation putting me at a higher risk of blood clots. Is it safe for me to have COVID-19 AstraZeneca?

    There is currently no evidence to suggest that having a medical condition which increases your likelihood of developing blood clots puts you at a greater risk of developing TTS following receipt of COVID-19 AstraZeneca.

    There is currently no evidence to suggest that having a history of atrial fibrillation predisposes you to developing thrombosis with thrombocytopenia syndrome (TTS) following receipt of an adenoviral vector vaccine such as COVID-19 AstraZeneca. In contrast, there is strong evidence that COVID-19 disease is thrombogenic (promotes clot development) and may cause a variety of thromboembolic events. TTS is a unique condition involving the development of thromboses (blood clots) combined with thrombocytopenia (low platelets).

    Individuals with a history of atrial fibrillation are encouraged to receive a COVID-19 vaccine when offered.

    Refer to the Joint statement from ATAGI and THANZ on Thrombosis with Thrombocytopenia Syndrome (TTS) and the use of COVID-19 Vaccine AstraZeneca for more information.

  • I am under 60 years of age and I just want to be vaccinated ASAP. Can I have COVID-19 AstraZeneca as it is more readily available?

    Whilst ATAGI preferentially recommends administration of an alternate brand of COVID-19 vaccine (Comirnaty™) in those aged under 60 years, it is not contraindicated. It is important to be informed of common, expected and rarer side effects of vaccination prior to receiving any vaccine. The risk of developing thrombosis with thrombocytopenia syndrome (TTS) following receipt of COVID-19 AstraZeneca is rare with current evidence suggesting a rate of approximately 4-6 cases per 1 million doses of the vaccine administered.

  • I am 61 years of age. Why is COVID-19 AstraZeneca deemed safe for me to receive?

    Like any arbitrary age cut-off, it is acknowledged that there may be limited difference between an individual at age 60 or 61 years. What we do know is that the risk of intensive care admissions and death increases markedly with age, with each decade of life increasing the risk 3-fold. Conversely, the possibility of thrombosis with thrombocytopenia syndrome (TTS) may be higher in younger people, based on currently available data.

    ATAGI have taken this data, along with safety data analysis from other countries such as the UK, other risks such as prevalence of COVID-19 in the Australian population along with any existing COVID-19 outbreaks, to calculate an age-specific benefit-to-risk balance for the Australian population. This has resulted in a current age cutoff of 60 years old in the current recommendations.

  • What is the risk-benefit ratio (also known as benefit-risk-assessment) when weighing up whether to get vaccinated?

    A benefit-risk assessment is important to conduct when recommending any vaccination. This measures the benefits of vaccination (eg. reduction of morbidity and mortality from the disease) to any potential risks. Also known as a benefit-risk ratio or balance, it will vary with other factors such as age, prevalence of outbreaks in a population and potential exposure to the disease in their workplace. This assessment may differ from individual to individual.

    For COVID-19, older people are at an increased risk of severe disease and death if they contract COVID-19. Younger people with underlying conditions such as immunocompromise, are also at an increased risk of severe disease, which affects their benefit-to-risk balance.

    The absence of COVID-19 in the community also affects this benefit-to-risk balance. Current advice would be reconsidered in the context of an outbreak, as the benefit in preventing COVID-19 would outweigh the risk for most adults.

    For more information on weighing up the potential benefits vs risk of harm please refer to Weighing up the potential benefits against risk of harm from COVID-19 AstraZeneca.

    Whilst the current recommendations in Australia are that Comirnaty™ is preferred vaccine for people under 60, a person in this age group can make an informed decision in conjunction with their healthcare provider to receive a COVID-19 AstraZeneca vaccine based on an understanding of their individual benefit-risk assessment.

  • Can I get a blood test to check my immune response from the first dose and avoid the need for a second dose?

    COVID-19 serology is not routinely available following vaccination and is not able to inform the decision to proceed with a second dose. Due to the novel nature of SARS-CoV-2, a correlate of protection has not yet been established for COVID-19 in humans.

    Data from clinical trials demonstrated that a 12-week interval between 2 doses of COVID-19 AstraZeneca provided a significant increase in the immune response and longer-term protection.

    Refer to COVID-19 vaccination- ATAGI clinical guidance on COVID-19 vaccine in Australia in 2021 for more information.

  • How much protection do I get from 1 dose of COVID-19 AstraZeneca?

    The level of protection gained from a single dose of COVID-19 AstraZeneca was assessed during clinical trials in an exploratory analysis that included participants who had received one dose. Protection was 73%, with the 95% CI from 49% and 86%, starting from 3 weeks after the first dose. This analysis reflects the short term efficacy and does not demonstrate the duration of protection. It is important to note that COVID-19 AstraZeneca is provisionally licensed by the Therapeutic Goods Administration as a two dose schedule.

    Refer to COVID-19 vaccination- ATAGI clinical guidance on COVID-19 vaccine in Australia in 2021 or COVID-19 AstraZeneca Product Information for more information.

  • I’m unsure about having COVID-19 AstraZeneca, can I wait for an alternate vaccine brand?

    There is no certainty regarding when additional alternate vaccine brands will be available in Australia.

    Whilst the Australian government have announced that an additional 20 million doses of Comirnaty™ have been secured, these will not be available until later in 2021.

    Similarly, an agreement is in place for the supply of the Moderna COVID-19 vaccine. This vaccine is yet to receive registration by the TGA and must be manufactured overseas before supply will reach Australia. This is not anticipated to occur until late 2021.

    There is an advance purchase agreement for the Novavax vaccine candidate which is still in phase III trials. Once trials have been completed, if proven safe and effective, this vaccine would still need to obtain provisional registration prior to any rollout in Australian. Doses of Novavax vaccine will be manufactured overseas and as such availability will be depend on the ability to import doses.

    In making a decision to delay vaccination it is important to be aware of the potential for a COVID-19 outbreak. While Australia currently has minimal community transmission of COVID-19, this can change quickly. Factors to consider include winter months approaching, high rates of global transmission, the emergence of new variants of the virus, as well as the potential for future changes to Australia’s border controls.

  • ATAGI have noted that “people of any age without contraindications who have had their first dose of COVID-19 Vaccine AstraZeneca without any serious adverse events should receive a second dose of the same vaccine``. What constitutes a serious adverse event?

    A serious adverse event following immunisation (AEFI) includes anaphylaxis or thrombosis with thrombocytopenia syndrome (TTS).

    Anaphylaxis to a previous dose of a vaccine is a contraindication to future doses of that same vaccine.

    As a precaution those with a past history of TTS, cerebral venous sinus thrombosis (CVST), heparin-induced thrombocytopenia (HIT), idiopathic splanchnic (mesenteric, portal and splenic) venous thrombosis, and anti-phospholipid syndrome with thrombosis are advised not to receive COVID-19 AstraZeneca.

    All adverse events should be reported to SAEFVIC. Specialist immunisation advice can be sought by referring patients to the VicSIS.

  • I am over 60 years of age and my GP has recommended that I be immunised with Comirnaty™. What happens now?

    Due to limits in supply of COVID-19 vaccines, distribution is currently based on the priority groups decided by the Commonwealth. Comirnaty™ is the preferred vaccine for those aged 16-59 years and COVID-19 AstraZeneca available for individuals 60 years and over.
    There are a very small subset of individuals over 60 years, who may also be recommended to receive a Comirnaty™. This currently is only the case for:
    • Individuals who have experienced a serious adverse event following a previous dose of COVID-19 vaccine (eg. thrombosis with thrombocytopenia syndrome (TTS) or immediate (within 2 hours) and generalised symptoms of possible allergic reaction to a previous dose of COVID-19 vaccine
    • An individual at higher risk of developing an adverse event following a COVID-19 vaccination such as:
      • Those with a history of cerebral venous sinus thrombosis (CVST), heparin-induced thrombocytopenia (HIT), idiopathic splanchnic (mesenteric, portal and splenic) venous thrombosis or anti-phospholipid syndrome with thrombosis
      • Anaphylaxis or generalised allergic reaction (without anaphylaxis) to any component of the COVID-19 vaccine to be administered
      • A history of PEG or polysorbate 80 related allergic reactions
      • A systemic mast cell activation condition with a raised tryptase who have been unable to tolerate previous intramuscular injections due to recurrent anaphylaxis.
    If you meet this criteria then you can be referred to a VicSIS clinic for assessment and immunisation advice prior to vaccination.

Authors: Daniela Say (MVEC Immunisation Fellow), Georgina Lewis (SAEFVIC Clinical Manager, Murdoch Children’s Research Institute), Rachael McGuire (MVEC Education Nurse Coordinator) and Francesca Machingaifa (MVEC Education Nurse Coordinator)

Reviewed by: Rachael McGuire (MVEC Education Nurse Coordinator) and Francesca Machingaifa (MVEC Education Nurse Coordinator)

Date: June 17, 2021

Materials in this section are updated as new information and vaccines become available. The Melbourne Vaccine Education Centre (MVEC) staff regularly reviews materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family’s personal health. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult a healthcare professional.