Australia’s trusted independent immunisation experts

Learn about the virus and the vaccines


There have been tens of thousands of confirmed cases of COVID-19 in Australia. Over 1,900 people have lost their lives.1 Most people will get better but about 12% of people with COVID-19 will need to go to hospital. Around 5% will still feel sick after 3 months.

  • What is COVID-19?

    Coronavirus disease 19 (COVID-19) was found in humans in December 2019 in China. It spreads from person to person by coughing, sneezing, speaking, singing or breathing, or after touching contaminated surfaces or objects.2 

    People usually start to feel unwell about 5–6 days after they get COVID-19.3 But this can range from 1 to 14 days.3 The most common signs of illness are headache, sore throat, cough, runny nose and fever.4 

    COVID-19 spreads easily. It was declared a worldwide pandemic by the World Health Organization (WHO) in March 2020.

  • 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 have ongoing illness (often called ‘long COVID’). In Australia, around 5% of people with COVID-19 will still feel unwell after 3 months.8 

The COVID-19 vaccines

Australia is likely to get different COVID-19 vaccines over time. There are two different types of vaccines approved for use in Australia:

  1. 'mRNA vaccines' which use a piece of code that has been genetically engineered; Comirnaty (Pfizer/BioNTech) and Spikevax (Moderna) are mRNA vaccines
  2. 'viral vector vaccines' which use genetic material taken directly from the spike protein and place it inside a harmless inactive virus; Vaxzeveria (AstraZeneca) is a viral vector vaccine.
  • 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 2 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.

  • 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.

  • 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 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.

  • 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.

  • Do the vaccines work for different variants?

    Yes, the currently approved vaccines are highly effective against existing variants, including the Delta variant, once two doses have been taken.

  • Do I need a booster? 

    A booster dose is recommended for everyone over the age of 18 years. Your first two doses will provide you with very good protection against the virus; however, protection fades with time. A booster dose 5 or more months after your second dose will give you greater, longer-lasting protection against COVID-19, including improved protection against the Omicron variant. 

  • 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

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

    Yes, there is now real-world evidence from many countries including the USA15-17 and Australia18 showing that mRNA COVID-19 vaccines (such as the Pfizer and Moderna vaccines) are safe for children 5 years of age and older.19,20 The side effects reported are similar to those reported in adults.15-18,20

    Children, particularly under the age of 10 years, are at a lower risk of getting COVID-19 than adults, but adolescents, especially older teenagers, seem to have the same risk of getting COVID-19 as young adults.21-22 

    The symptoms of COVID-19 are usually milder in children than in adults but it can still very rarely cause severe illness. Around 98% of children and adolescents either get mild infection or have no symptoms at all.23,24 However, some children need to go to hospital and a smaller number to intensive care. Studies show that children and adolescents with underlying medical conditions have a greater risk of developing severe disease and complications from COVID-19.23-25

+ References

  1. Australian Government Department of Health. Coronavirus (COVID-19) current situation and case numbers; Available from: 
  2. WHO. Transmission of SARS-CoV-2: implications for infection prevention precautions. Scientific brief. [Internet.] Geneva: WHO; 9 July 2020. Available from:
  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:
  4. Zoe COVID Study. What are the top 5 COVID symptoms? 2021. Available from: 
  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:
  6. Rothan HA, Byrareddy SN. The epidemiology and pathogenesis of coronavirus disease (COVID-19) outbreak. J Autoimmun. 2020;109. doi:  
  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:
  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. 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.
  15. Centers for Disease Control and Prevention (CDC). COVID-19 Vaccine Safety in Adolescents Aged 12–17 Years — United States, December 14, 2020–July 16, 2021. 2021. Available from: (Accessed 16 November 2021).
  16. Ali K, Berman G, Zhou H, et al. Evaluation of mRNA-1273 SARS-CoV-2 Vaccine in Adolescents. New England Journal of Medicine 2021.
  17. Frenck RW, Jr., Klein NP, Kitchin N, et al. Safety, immunogenicity, and efficacy of the BNT162b2 Covid-19 vaccine in adolescents. New England Journal of Medicine 2021; 385:239-50.
  18. National Centre for Immunisation Research and Surveillance (NCIRS). AusVaxSafety COVID-19 vaccine safety data. 2021. Available from: (Accessed 16 November 2021).
  19.  Australian Technical Advisory Group on Immunisation (ATAGI). ATAGI recommendations on Pfizer COVID-19 vaccine use in children aged 5 to 11 years. Available from: Accessed 15 December 2021
  20. Walter EB, Talaat KR, Sabharwal C, et al. Evaluation of the BNT162b2 Covid-19 Vaccine in Children 5 to 11 Years of Age. New England Journal of Medicine. 2021;0(0):null. doi:10.1056/NEJMoa2116298
  21. Molteni E, Sudre CH, Canas LS, et al. Illness duration and symptom profile in symptomatic UK school-aged children tested for SARS-CoV-2. The Lancet Child & Adolescent Health 2021.
  22. Götzinger F, Santiago-García B, Noguera-Julián A, et al. COVID-19 in children and adolescents in Europe: a multinational, multicentre cohort study. The Lancet Child & Adolescent Health 2020; 4:653-61.
  23. Assaker R, Colas AE, Julien-Marsollier F, et al. Presenting symptoms of COVID-19 in children: a meta-analysis of published studies. Br J Anaesth 2020; 125:e330-e2.
  24. Poline J, Gaschignard J, Leblanc C, et al. Systematic Severe Acute Respiratory Syndrome Coronavirus 2 Screening at Hospital Admission in Children: A French Prospective Multicenter Study. Clinical Infectious Diseases 2021; 72:2215-7.
  25. Kompaniyets L, Agathis NT, Nelson JM, et al. Underlying medical conditions associated with severe COVID-19 illness among children. JAMA Network Open 2021; 4:e2111182.
  26. Graff K, Smith C, Silveira L, et al. Risk factors for severe COVID-19 in children. Pediatric Infectious Diseases Journal 2021; 40:e137-e45.
  27. American Academy of Pediatrics. Children and COVID-19: State-Level Data Report. 2021. Available from: (Accessed 16 November 2021).