Learn about the virus and the vaccines


There have been millions of confirmed cases of COVID-19 in Australia. Thousands of people have lost their lives.1 Most people who catch COVID-19 will get better; however, some will get so sick they need to go to hospital or be cared for by hospital staff in a 'hospital at home' program. A small number will still feel sick three months or more after they first catch COVID-19.

  • What is COVID-19?

    Coronavirus disease 19 (COVID-19) was found in humans in December 2019 and was declared a worldwide pandemic by the World Health Organization (WHO) in March 2020.

    It spreads easily and can be passed from person to person through coughing, sneezing, speaking, singing or breathing, or after touching contaminated surfaces or objects.2

    People usually start to feel unwell about five to six days after they get COVID-19,3 but it can be anywhere from one to 14 days.3 The most common signs of illness are headache, sore throat, cough, runny nose and fever.4

    A number of different versions or 'variants' of COVID-19 have emerged since the virus was first detected. These include Delta and Omicron. The vaccines available in Australia all offer protection against COVID-19 variants.

  • What are the risks of COVID-19?

    COVID-19 has killed millions of people around the world. Most people get better without needing medical help. Some people have more serious outcomes, such as breathing difficulties and pneumonia (lung infection). They may need to go to hospital for extra oxygen or ventilation (where a machine helps you breathe).5,6 Serious illness or death is more common among older adults or those with other health problems.7  

    Some people will experience symptoms including headache, fatigue, sleep problems and difficulty concentrating, for three months or more. This condition is often called 'long COVID'.

COVID-19 vaccination

COVID-19 vaccines train our bodies to recognise and fight the virus. They do this by teaching our immune system to read the genetic code for an important part of the virus, called the spike protein. 

Vaccination means you will be less likely to catch COVID-19 and pass it on to others. There is still a small chance that you will catch the virus, but if you do, your symptoms will usually be mild.

Australia is likely to get different COVID-19 vaccines over time. 

The vaccines currently approved for adults in Australia are: 

  • Pfizer/BioNTech (Comirnaty) 
  • Moderna (Spikevax)
  • AstraZeneca (Vaxzeveria) 
  • Novavax (Nuvaxovid) 
  • How do the COVID-19 vaccines work?

    The vaccines contain the genetic code for an important part of the COVID-19 virus called the spike protein. Spike proteins are found on the outside of the virus. Their job is to fuse to the outside of your cells, so the virus can enter your cells and cause illness.

    When you get the vaccine, your body reads this genetic code and trains your immune system to recognise the spike proteins and fight the virus. Within about two weeks of vaccination, your body will start making antibodies. After that, if you come into contact with the COVID-19 virus, these antibodies will attach to it and help get rid of it.

    You cannot catch COVID-19 from the vaccines because they don't contain the virus. They only contain the genetic code required to train your immune system to recognise and fight it.

    Different vaccines work with the genetic code in different ways. 

    mRNA vaccines use a piece of code that has been genetically engineered. Australian health authorities have approved the use of the following mRNA vaccines: 

    • Pfizer/BioNTech (Comirnaty) 
    • Moderna (Spikevax) 

    Viral vector vaccines use genetic material taken directly from the spike protein and place it inside a harmless inactive virus. Australian health authorities have approved the use of the following viral vector vaccines:

    • AstraZeneca (Vaxzeveria) 

    Protein subunit vaccines use a harmless version of the spike protein to stimulate an immune response in your body. Australian health authorities have approved the use of the following protein subunit vaccines:

    • Novavax (Nuvaxovid) 
  • How were the COVID-19 vaccines tested?

    Safety research is a key part of making vaccines. Vaccines are tested extensively before they are ready for use. Testing begins with research in a lab (test tubes), then animal studies and finally studies in humans (clinical trials).

    Clinical trials involve testing the vaccine in volunteers, and run in three main phases:

    Phase 1 clinical trials usually involve a few dozen healthy adult volunteers. These trials focus on vaccine safety and finding out if the vaccine causes an immune response.

    Phase 2 clinical trials are bigger and have hundreds of volunteers. These trials test the immune response of the vaccine among a larger group of people, and assess whether it is safe, with acceptable side effects. 

    Phase 3 clinical trials involve many thousands of participants. These trials assess how effective the vaccine is at preventing people from getting the disease. Phase 3 trials can more thoroughly assess the vaccine for safety and side effects. In a Phase 3 trial, researchers usually compare people who received the vaccine with people who didn’t.

    Typically, these phases happen one after the other. For the development of the COVID-19 vaccines, some of the phases overlapped. For example, Phase 3 studies were started as soon as early data from Phase 1 and 2 trials became available. This approach meant the COVID-19 vaccines could be developed quickly, making them available to save lives sooner.

  • What are the benefits of having a COVID-19 vaccine?

    Having the vaccine means you will be less likely to catch COVID-19 and pass it on to others. If you’re vaccinated, you’ll be able to visit vulnerable or older family members more safely. You’ll also be able to travel for work or holidays, and schools and workplaces will be safer.

    There is still a small chance that you will catch COVID-19, but if you do, your symptoms will usually be mild.

    If you want to know more about the benefits of vaccination for a child, we recommend that you use the COVID-19 Decision Aid (5-15 years).

  • What are the risks of having a COVID-19 vaccine?

    Most people have mild symptoms for a day or two after a COVID-19 vaccine. This is completely normal and may include pain or tenderness at the injection site, headache, tiredness, chills, muscle or joint pain.9 Serious side effects are very rare. We will provide more detail about the risks of vaccination side-effects in the next step of this decision aid.

    You may have heard people talk about other risks associated with COVID-19 vaccines. These are not mentioned here because there is no scientific evidence to support them.

    If you want to know more about the risks of vaccination for a child, we recommend that you use the COVID-19 Decision Aid (5-15 years).

  • Do the vaccines work for different variants?

    Yes. The currently approved vaccines are highly effective against existing variants. There is still a chance that you will catch the virus, but if you do, your symptoms will usually be mild.

  • Do I need a booster?

    A booster dose is recommended for everyone over the age of 16 years. The effectiveness of your original vaccination will fade over time. Having a booster shot will make sure you continue to be protected against the virus.

  • If I have had COVID-19, do I still need the vaccine and boosters?

    Yes. If you have tested positive to COVID-19, your chance of reinfection will be reduced, but only for a few months. 

    To keep up your protection against the virus, it is recommended that you get a booster shot within four months of recovering from acute illness. 

  • Is it safe for pregnant women to have a COVID-19 vaccine?

    Yes, there is now real-world evidence from countries such as the USA showing that mRNA COVID-19 vaccines (such as the Pfizer and Moderna vaccines) are safe for pregnant women.10-11 The side effects reported are similar to those reported in non-pregnant women.11

    COVID-19 vaccination is recommended for pregnant women because research has shown they have a higher risk of severe illness from the virus. In particular, women with COVID-19 who are pregnant are more likely to be admitted to an intensive care unit and more likely to need a machine to help them breathe (ventilation) than those who have COVID-19 and aren't pregnant.12-14

    Having COVID-19 while you're pregnant can also increase your risk of birth complications. Pregnant women who have the virus are more likely to deliver their babies early than those who don't have the virus. They may also be more likely to have stillbirths.6

+ References

  1. Australian Government Department of Health. Coronavirus (COVID-19) current situation and case numbers; Available from: https://www.health.gov.au/news/health-alerts/novel-coronavirus-2019-ncov-health-alert/coronavirus-covid-19-current-situation-and-case-numbers#at-a-glance 
  2. WHO. Transmission of SARS-CoV-2: implications for infection prevention precautions. Scientific brief. [Internet.] Geneva: WHO; 9 July 2020. Available from: https://www.who.int/news-room/commentaries/detail/transmission-of-sars-cov-2-implications-for-infection-prevention-precautions
  3. McAloon C, Collins Á, Hunt K, Barber A, Byrne AW, Butler F et al. Incubation period of COVID-19: a rapid systematic review and meta-analysis of observational research. BMJ Open. 2020;10(8). doi: https://doi.org/10.1136/bmjopen-2020-039652
  4. Zoe COVID Study. What are the top 5 COVID symptoms? 2021. Available from: https://covid.joinzoe.com/post/new-top-5-covid-symptoms#part_3 
  5. Australian Government Department of Health. Australian National Disease Surveillance Plan for COVID-19. [Internet.] Canberra: Australian Government Department of Health; 30 May 2020. Available from: https://www.health.gov.au/resources/publications/australian-national-disease-surveillance-plan-for-covid-19.
  6. Rothan HA, Byrareddy SN. The epidemiology and pathogenesis of coronavirus disease (COVID-19) outbreak. J Autoimmun. 2020;109. doi: https://doi.org/10.1016/j.jaut.2020.102433  
  7. Hu Y, Sun J, Dai Z, Deng H, Li X, Huang Q et al. Prevalence and severity of corona virus disease 2019 (COVID-19): A systematic review and meta-analysis. J Clin Virol. 2020;127. doi: https://doi.org/10.1016/j.jcv.2020.104371.
  8. Liu B, Jayasundara D, Pye V, Dobbins T, Dore GJ, Matthews G, Kaldor J, Spokes P. Whole population-based cohort study of recovery time from COVID-19 in New South Wales, Australia. The Lancet Regional Health-Western Pacific. 2021;1(12):100193.
  9. National Centre for Immunisation Research and Surveillance. AusVaxSafety. 2021. https://www.ausvaxsafety.org.au/ accessed August 2021. 
  10. Akhtar H, Patel C, Abuelgasim E, Harky A. COVID-19 (SARS-CoV-2) infection in pregnancy: a systematic review. Gynecologic and Obstetric Investigation. 2020;85(4):295-306.
  11. Ciapponi A, Bardach A, Mazzoni A, Alconada T, Anderson AS, Argento FJ, Ballivian J, Bok K, Comandé D, Erbelding E, Goucher E. Safety of components and platforms of COVID-19 vaccines considered for use in pregnancy: A rapid review. Vaccine. 2021 Aug 13.
  12. Zambrano  LD, Ellington  S, Strid  P,  et al.  Update: characteristics of symptomatic women of reproductive age with laboratory-confirmed SARS-CoV-2 infection by pregnancy status—United States, January 22-October 3, 2020.   MMWR Morb Mortal Wkly Rep. 2020;69(44):1641-1647.
  13. Wei SQ, Bilodeau-Bertrand M, Liu S, Auger N. The impact of COVID-19 on pregnancy outcomes: a systematic review and meta-analysis. CMAJ. 2021;193(16):E540-8.
  14. Shimabukuro, Tom T., et al. Preliminary findings of mRNA Covid-19 vaccine safety in pregnant persons. New England Journal of Medicine. 2021; 384(24): 2273-2282.