These COVID-19 vaccine FAQs have been designed to address common queries relating to COVID-19 vaccine development, safety, effectiveness and storage.

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.

Vaccine development process

  • How can the COVID-19 vaccine be safe when it has been developed so quickly?

    COVID-19 vaccine development has happened “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.

  • What is involved in the phases of clinical trials?

    During vaccine development, initial safety testing of a vaccine candidate occurs in two stages. Stage one involves preclinical assessment both in the laboratory and also animal trials.  Stage two involves the evaluation of the vaccine candidate in three phases of clinical trials in human volunteers.

    Phase I clinical trials: the vaccine candidate is given to small numbers (25–50) of healthy adults with the primary goal of assessing safety.

    Phase II clinical trials: If the vaccine candidate is found to be safe in Phase I, it is then given to hundreds of participants to determine how effectively it stimulates immune responses; optimal dose regimen; and its side effect profile.

    Phase III clinical trials: If the vaccine candidate is found to be effective and safe in both Phase I and II, it is then given to many thousands of participants to test its effect on protecting large populations from the target disease and to determine if there are any uncommon, serious or severe side effects.

    Refer to MVEC: Vaccine development and safety for more information.

  • What does provisional approval mean and how does it differ from normal registration?

    The Therapeutic Goods Administration (TGA) is responsible for approving and regulating all medicines, including vaccines, used within Australia.

    Due to the urgent need for COVID-19 vaccines to prevent morbidity, mortality and disease transmission, vaccine sponsors have been able to apply for ‘provisional registration’ which allows the rollout of a vaccine to occur more quickly. Vaccines can be provisionally approved for use based on preliminary clinical trial data, where the benefits of earlier access to a vaccine have been determined to outweigh potential risks of waiting for additional data. Sponsors may then apply for ‘full registration’ when more clinical data is available.

    Refer to MVEC: Provisional registration of COVID-19 vaccine(s) in Australia and TGA: COVID-19 vaccines for further information.

  • How can we be sure that the vaccine 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, safety, affectiveness and quality continues to be monitored in the post-licensure phase.

  • Who funds a vaccine trial?

    Vaccine research and development is often funded by a range of sources including governments, bilateral and multilateral organisations, non-government organisations and the private sector (including pharmaceutical companies). Never before has one vaccine received so much investment and global collaboration – this is a major reason why there are multiple COVID-19 vaccines that have been able to progress so efficiently with minimal pauses through to the final phase III large clinical trials.

    A prominent funding source for many COVID-19 vaccines is the COVAX Facility. COVAX is coordinated by Gavi (the Vaccine Alliance), the Coalition for Epidemic Preparedness Innovations (CEPI) and the World Health Organization. COVAX pools funding from over 180 governments, global health organisations, private sector and manufacturers to support research, development and manufacturing of multiple COVID-19 vaccine candidates.

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?

    Minor side effects following COVID-19 vaccination are expected. Common symptoms 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.

    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 COVID-19 vaccines be given to people who are immunosuppressed?

    It is recommended that all individuals aged 12 and over with immunosuppression receive COVID-19 vaccines. Having a lowered immune system increases the likelihood of developing severe disease and complications if infected with SARS-CoV-2. Due to the restricted eligibility criteria in early vaccine clinical trials, there is currently minimal data on the safety and efficacy of COVID-19 vaccination in this group. In principle, there are no theoretical safety risks and no vaccine safety signals have been identified for people with immunocompromise to date.

    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 – Provider guide to COVID-19 vaccination of people with immunocompromise for more information.

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

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

    Surveillance of Adverse Events Following Vaccination In the Community (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.

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

    Any event felt to be significant following immunisation should be reported. You do not need to routinely report common/minor/expected reactions.

    Clinicians must report severe adverse effects through SAEFVIC in Victoria. This should be done whether you think the side effect was related to the vaccine or not.

  • I experienced side effects from the first dose of the vaccine, should I have the second dose?

    Common side effects that are short lived are not a contraindication to further doses of COVID-19 vaccines.

    If you have experienced any unanticipated side effects following a vaccine, it should be discussed with your GP and reported to SAEFVIC.

  • 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 refer to MVEC: Vaccine-associated enhanced disease.

Effectiveness

  • How do we know a vaccine is effective?

    In vaccine clinical trials it is important to understand the difference between efficacy versus effectiveness. Efficacy is calculated from a Phase III clinical trial and effectiveness is the vaccine’s impact in a real world setting once the vaccine is administered in the general public.

    Vaccine clinical trials represent a strictly controlled setting; for example, trial participants are closely monitored and if two vaccine doses are required, the doses will be given with exactly the same interval for everyone. All vaccines that are eventually registered will have proved they have adequate efficacy through large Phase III trials.

    Efficacy is calculated by assessing how many people develop COVID-19 in the group receiving the COVID-19 vaccine compared to the placebo (or control) group. For example, if 100 people develop COVID-19 disease in a trial, and 95 of these were in the placebo group (meaning only 5 people in the vaccine group developed disease), the vaccine efficacy would be calculated at 95%. In other words, the vaccine prevented 95 out of 100 people from contracting COVID-19 disease. Efficacy is usually calculated after the full vaccine course; for most COVID-19 vaccines this is after two doses.

    In a real-world setting, it is expected that there will be lower levels of protection due to multiple variables, such as wider differences amongst people receiving the vaccine (eg. different ethnicities or underlying medical conditions). Hence vaccine effectiveness is expected to be slightly lower than what is reported in initial clinical trial results. Vaccine effectiveness in the real world will continue to be monitored in post-licensure studies.

  • Will the vaccine be effective in children?

    Currently, COVID-19 vaccines are not registered for use in Australia in children aged less than 12 years. To date, COVID-19 infections have produced more severe disease outcomes in adults and the older population, with children generally experiencing milder symptoms. For this reason, initial COVID-19 vaccine clinical trials and vaccine rollouts have focused on the adult population.  

    Clinical trials are currently underway to determine the safety and efficacy of various COVID-19 vaccines in children. For more information, please refer to our reference page COVID-19 vaccination in children

  • Can the vaccine be given to people who are immunosuppressed?

    It is recommended that all individuals aged 12 and over with immunosuppression receive COVID-19 vaccines. Having a lowered immune system increases the likelihood of developing severe disease and complications if infected with SARS-CoV-2. Due to the restricted eligibility criteria in early vaccine clinical trials, there is currently minimal data on the safety and efficacy of COVID-19 vaccination in this group. In principle, there are no theoretical safety risks and no vaccine safety signals have been identified for people with immunocompromise to date.

    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 – Provider guide to COVID-19 vaccination of people with immunocompromise for more information.

  • What is herd immunity?

    Herd immunity describes when a certain proportion of the community is immune to a specific pathogen (in this case virus). It can only be induced by vaccination; never in history has any virus infection been eliminated because of immunity by natural infection.

    Herd immunity is achieved when more than 60-70% of people in a population are vaccinated against a particular illness. At this level of population immunity, there are fewer people that the pathogen can infect and hence this self-limits the spread of the pathogen.

    Please see more information about herd immunity from the Australian Academy of Science.

  • Can COVID-19 vaccines be used to prevent disease in patients who have already been identified as contacts of a COVID-19 positive case?

    COVID-19 vaccine administration is not recommended for post-exposure prophylaxis.

    Please refer to COVID-19 vaccination – ATAGI clinical guidance on COVID-19 Vaccine in Australia in 2021 for more information.

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

    There is some evidence that one dose of Comirnaty (Pfizer) or Spikevax (Moderna) 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 recommended in Australia?

    A single booster dose is recommended for individuals ≥ 18 years, if ≥ 6 months has passed since the completion of a primary course of COVID-19 vaccination.

    Comirnaty (Pfizer) is the preferred brand for a booster doses (regardless of the brand used for the primary course) however Vaxzevria (AstraZeneca) may be used in certain circumstances. These include where an individual received Vaxzevria (AstraZeneca) as their primary course without any serious adverse event, or where a serious adverse event occurred following the administration of Comirnaty (Pfizer) and an alternate brand is recommended. Data on the use of Spikevax (Moderna) as a booster dose is currently being evaluated.

    For further information refer to ATAGI recommendations on the use of a booster dose of COVID-19 vaccine.

     

Storage

  • How should COVID-19 vaccines be stored?

    The storage environments required for the COVID-19 vaccines being used within Australia vary depending on the brand of vaccine.

    mRNA vaccines (Comirnaty (Pfizer) and Spikevax (Moderna)) require ultra-low cold chain storage and transport conditions, resulting in additonal logistical considerations for purpose built freezers and dry ice. Once defrosted they will only remain stable for a limited amount of time.

    Vaxzevria (AstraZeneca) and the Novavax COVID-19 vaccine candidate can be stored in standard vaccine cold chain temperatures of between 2°C to 8°C.

    For more information on cold chain please refer to MVEC: Cold chain.

  • Are multi-dose vials safe? Why are they being used?

    Multi-dose vials (MDV) are safe as long as each dose is prepared appropriately using aseptic technique. They should be kept and accessed in a dedicated clean medication preparation area and away from immediate patient treatment areas. This is to prevent inadvertent contamination of the vial and cross contamination between patients.

    MDVs are cheaper to produce and occupy less cold-chain capacity. In the context of the COVID-19 pandemic; improved efficiency of production and storage is vital when millions of doses must be produced quickly.

    To learn how to safely prepare and store multi-dose vials please refer MVEC: Multi-dose vials.

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

Date: November 3, 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.