These COVID-19 vaccine FAQs have been designed to address common queries relating to mRNA vaccines.

Please also see our other COVID-19 FAQs for more information on other COVID-19 related 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 contact us here.


  • How do mRNA vaccines work?

    mRNA and DNA vaccines are genetic vaccines. They allow the genetic material of viral proteins (small parts of a pathogen) to be recreated by human cells as an antigen. Once the antigen has been identified by the immune system, antibodies and memory cells are produced to provide protection against future infection.

    Although DNA and mRNA vaccines had not been licensed prior to the COVID-19 pandemic, they were already under development for other viruses, such as influenza.

  • How long has mRNA technology been available for?

    There has been some concern amongst the public regarding the speed of development of mRNA COVID-19 vaccines. When in fact, researchers have been studying and working with mRNA technology for over 30 years. Since its discovery in 1961, mRNA has been the subject of research for various diseases.

    Further information regarding the timeline of key discoveries and advances in the development of mRNA as a drug technology can also be seen at Nature: mRNA-based therapeutics- developing a new class of drugs.

  • What other diseases do we use mRNA technology for?

    mRNA therapeutics hold great promise in the management of numerous human diseases including infections, cancers and genetic disorders. An overview of mRNA therapeutics in preclinical and clinical stages including their application can be seen here. Clinical experience is predominately in cancer immunotherapy but has expanded rapidly following the global use of the COVID-19 mRNA vaccines. As a result, the excellent tolerability and safety profile that has been demonstrated is limited to their current clinical use.

  • Can mRNA vaccines alter my DNA?

    No. It is not possible to integrate vaccine mRNA into an individual’s own DNA. mRNA from vaccines are unable to enter the nucleus of a human cell (where a person’s genetic material is stored). It is also not possible for vaccine mRNA to revert to DNA. In addition, mRNA from COVID-19 vaccines only provide the code for part of the pathogen (eg. the spike protein on the outer surface of a SARS-CoV-2 virus) and not the whole pathogen.

    For more information refer to CHOP: Can mRNA vaccines alter a persons DNA?

  • Do COVID-19 vaccines cause viral shedding?

    None of the COVID-19 vaccines used within Australia contain live virus and therefore people who are vaccinated cannot shed or transmit the virus to other people.

    COVID-19 disease itself is highly infectious and can be transmitted via respiratory secretions.

  • What ingredients are NOT in mRNA COVID-19 vaccines?

    The following products are NOT ingredients in mRNA COVID-19 vaccines:

    • Animal products
    • Antibiotics
    • Blood products
    • DNA
    • Egg proteins
    • Foetal material
    • Gluten
    • Microchips
    • Pork products
    • Thiomersal
    • Soy
    • Latex
    • Aluminium

    Further information can be found in the vaccine product information:

  • What other diseases do we use mRNA technology for?

    mRNA therapeutics hold great promise in the management of numerous human diseases including infections, cancers, genetic disorders and even allergy desensitisation. To date, clinical experience has been predominately in cancer immunotherapy but this technology has expanded rapidly following the global use of the COVID-19 mRNA vaccines.

Pre-existing conditions

  • Can people with pre-exisiting cardiac (heart) conditions receive COVID-19 vaccines?

    Individuals with the following cardiac conditions can safely receive COVID-19 vaccines without the need for additional monitoring or precautions:

    • coronary artery disease
    • myocardial infarction
    • stable heart failure
    • arrhythmias
    • rheumatic fever
    • rheumatic heart disease
    • kawasaki disease
    • most congenital heart disease
    • those with implanted cardiac devices
    • congenital heart disease
    • cardiac transplant
    • cardiomyopathy.

    Those with a history of the following conditions can also receive COVID-19 vaccines; however should consult their treating specialist to determine the appropriate timing for vaccination:

    • recent (within 3 months) or current inflammatory cardiac conditions (including myocarditis, pericarditis and endocarditis)
    • acute rheumatic fever or acute rheumatic heart disease
    • acute decompensated heart failure.
  • What are the vaccine recommendations for people who have previously been diagnosed with myocarditis or pericarditis?

    Individuals with recent (within 3 months) or current inflammatory cardiac conditions (including myocarditis, pericarditis and endocarditis) can still receive COVID-19 vaccines however should consult their treating specialist before doing so to determine the best time to be immunised.

    For individuals in whom the cause of inflammation is attributed to COVID-19 vaccination, future dose recommendations depend on the diagnosis (myocarditis or pericarditis), a person’s age and the level of certainty of diagnosis.

    Individuals who have experienced myocarditis (the more serious adverse event following immunisation) attributed to a COVID-19 vaccination, a report to SAEFVIC is indicated. A referral to a cardiologist or specialist immunisation service prior to the administration of future doses may also be recommended.

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

    Yes. The COVID-19 vaccines currently in use within Australia are non-live vaccines and therefore can be administered at anytime following a blood transfusion.

    Patients with a past history of COVID-19 infection, who received monoclonal antibodies or convalescent plasma as part of their treatment, should wait a minimum of 3 months before considering vaccination.

    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.

  • When should people who have previously tested positive for COVID-19 disease be vaccinated?

    COVID-19 vaccination should be deferred 3 months following COVID-19 infection in order to optimise protection.

    Recommended COVID-19 vaccine schedules should be completed after this time.

    For further information, refer to the Clinical recommendations for COVID-19 vaccines.

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

    Yes. COVID-19 vaccination is recommended 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.

    For more information please refer to – Swollen Lymph Nodes Under Armpit After COVID-19 Vaccine May Mimic Breast Cancer Symptoms—Here’s What to Know and Peter Mac COVID:19 vaccination: frequently asked questions.

  • Are anthracycline therapies considered a contraindication to mRNA COVID-19 vaccines due to the association with myocarditis/pericarditis?

    Children who have been treated with chemotherapeutic agents including anthracyclines as part of their cancer therapy are not considered as higher risk of side effects from vaccination (including the development of myocarditis/pericarditis. Parents/guardians should speak to their treating team regarding COVID-19 vaccination based on current recommendations.

    For further information refer to COVID-19 Vaccination Guidance for children 12 years and older undergoing cancer treatment and children with non-cancerous blood disorders.

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

    Individuals who have previously been diagnosed with GBS can receive COVID-19 vaccines. Ongoing surveillance by the TGA and other international vaccine regulators has shown growing evidence of a possible link between GBS and Vaxzevria (AstraZeneca). Specialist advice from a treating neurologist or immunisation specialist may be considered to discuss the benefits and risks of vaccination.

    For more information please refer to MVEC: Guillain-Barre Syndrome and Victorian COVID-19 vaccination guidelines.

  • 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 Multiple Sclerosis (MS) to be immunised against COVID-19 disease?

    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 MS Australia: COVID-19 vaccination guidance for people with MS and MVEC: COVID-19 vaccines in people with immunocompromise.

  • 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.

    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 Australian Immunisation Handbook: Adverse events following immunisation or MVEC: COVID-19 vaccines and allergy.

  • Can COVID-19 vaccines be given to immunosuppressed individuals?

    It is recommended that all age-eligible individuals with immunosuppression receive COVID-19 vaccines. Additional doses are recommended for some individuals identified with severe immune suppression. Having a lowered immune system increases the likelihood of developing severe disease and complications if infected with SARS-CoV-2.

    People with immunocompromise receiving COVID-19 vaccination should be counselled about the possibility of reduced efficacy and the need to continue other preventative measures such as social distancing, mask wearing and hand hygiene. Household contacts should be encouraged to receive the COVID-19 vaccine when it is offered because vaccination has also been shown to reduce transmission.

    Please refer to ATAGI recommendations on the use of a third primary dose of COVID-19 vaccine in individuals who are severely immunocompromised for more information.

  • 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 (Pfizer) and Spikevax (Moderna). 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 or Spikevax is contraindicated in people with documented anaphylaxis to PEG.

    To read more refer to Australian Government Department of Health: COVID-19 vaccine contraindications and precautions.

  • Can I get COVID-19 vaccines if I have dermal fillers?

    It is safe and recommended for people who have previously received dermal fillers to receive COVID-19 vaccines.

    Individuals with a history of dermal filler injections can experience swelling at the site of the filler injection following viral or bacterial infections, dental procedures and some vaccines (ie. influenza and COVID-19 mRNA vaccines). International reports following COVID-19 mRNA vaccines indicate that any symptoms experienced following vaccination are likely to occur within 1-2 days and are temporary.

    As a precaution, an interval of 4-6 weeks between filler injections and vaccination may be considered.

    For more information please refer to Coronavirus vaccine – weekly summary of yellow card reporting.

Authors: Daryl Cheng (Medical Lead, MVEC), Rachael McGuire (MVEC Education Nurse Coordinator) and Francesca Machingaifa (MVEC Education Nurse Coordinator)

Reviewed by: Rachael McGuire (MVEC Education Nurse Coordinator)

Date: October 6, 2022

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.