How do I know the vaccines are safe?

Key facts

  • Safety research and testing are essential to developing vaccines. Their aim is to identify any uncommon or serious side effects related to vaccination.

  • Every vaccine given to Australian adolescents must pass three phases of research testing (clinical trials) before it is registered for use by the Therapeutic Goods Administration (TGA). The TGA reviews and evaluates the safety and quality of every vaccine ingredient before a vaccine is registered for use.  

  • Safety research, testing and monitoring are carried out for any vaccine recommended for adolescents. The TGA studies any suspected problem with a vaccine thoroughly.

Last updated on 13 August 2025.

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Could there be long-term side effects we don’t know about?

All vaccines go through lengthy and rigorous testing processes and must pass through three phases of research testing (clinical trials) to ensure they are safe before they are approved for use in Australia.

Research testing and clinical trial results are evaluated by many expert groups, including the Therapeutic Goods Administration (TGA) in Australia, the Food and Drug Administration (FDA) in the United States (US) and the World Health Organization’s Global Advisory Committee on Vaccine Safety. These and other expert groups continue to monitor all recommended vaccines to ensure they are safe and effective.1,2,3

Overall, many research studies show that all the routine vaccines recommended for your adolescent have an excellent safety profile.4,5,6,7,8 This means there is research and evidence to support that the vaccines are safe and do not cause any long-term side effects.

Unfortunately, some adolescents are diagnosed with long-term medical conditions or health problems. Research studies about vaccines given through the National Immunisation Program show that vaccinated and unvaccinated adolescents have similar rates of long-term medical conditions. No evidence shows that vaccination increases the risk of long-term medical conditions in adolescents.6,7,8

What happens if a problem with a vaccine is suspected?

Healthcare providers, parents and carers are encouraged to report any possible vaccine side effects their adolescent experiences to the TGA and the relevant health authority in their state or territory. 

One national vaccination safety service reviewing this information is AusVaxSafety. AusVaxSafety is led by the National Centre for Immunisation Research and Surveillance (NCIRS) and funded by the Australian Government Department of Health, Disability and Ageing. It is a vaccine safety surveillance system that monitors the safety of vaccines in Australia, including adverse events following vaccination that are unusual or unexpected. This information can also be reviewed by the Australian Government Department of Health, Disability and Ageing and other agencies including the TGA. 

When the TGA receives information that there are safety concerns about a vaccine, the issue is studied immediately and more information is collected.9 These studies usually involve more tests of vaccine quality and how the vaccines are being made (manufacturing processes). Vaccine experts may also study vaccinated and unvaccinated people who have and have not had reactions. This supports continuing vaccine safety.

If a suspected problem could be serious, authorities will consider a range of actions. For example, when human papillomavirus (HPV) vaccination was introduced for females in 2007, collected safety monitoring information showed a higher rate of fainting (syncope) than previously observed after vaccination in young adolescents.10 Because of this, extra steps were put in place to lower and prevent the risk of adolescents fainting before or during school vaccination.

Other actions can include suspending the use of a vaccine during an investigation. In 2010, experts found one brand of influenza (flu) vaccine (Seqirus/bioCSL Fluvax and Fluvax Junior) caused fits or seizures (febrile convulsions) in children aged under 5 years more often than other flu vaccine brands. That brand of influenza vaccine is no longer registered for use in children under 5 years of age and other seasonal flu vaccines are recommended for infants and young children.

Can my adolescent catch a disease from a vaccine?

No, there is no risk your adolescent will catch a disease from a vaccine given as part of routine adolescent vaccination. This is because the routine adolescent vaccines given as part of Australia’s National Immunisation Program don’t contain the live viruses that may cause disease. 

In the days after some vaccines – and especially flu vaccines – experiencing symptoms that feel like early flu infection is normal. While these side effects can look like the flu, they are a sign that your adolescent’s immune system is responding to the vaccine – which is exactly what’s supposed to happen. Also, it takes about two weeks for the vaccine to start protecting your adolescent – so if your adolescent caught the virus before they were vaccinated (but wasn’t feeling sick yet) or in the two weeks after they were vaccinated, it might seem like the vaccine made them sick.

More information about safety monitoring in Australia

If you would like to find out more information about vaccine safety monitoring in Australia, visit AusVaxSafety.

Please note: In SKAI Adolescent, the phrase ‘your adolescent’ refers to all guardian relationships where health decisions for an adolescent fall under your responsibility.

Drafts of this page were reviewed by members of our Consumer Advisory Group.


  1. Australian Government Department of Health and Aged Care: Therapeutic Goods Administration. Therapeutic Goods Administration. 2025. Available from 
    www.tga.gov.au
  2. United States Government: US Food & Drug Administration. US Food & Drug Administration. 2025. Available from www.fda.gov
  3. World Health Organization. Global Advisory Committee on Vaccine Safety (GACVS). 2025. Available from https://www.who.int/teams/regulation-prequalification/regulation-and-safety/pharmacovigilance/networks/vaccine-safety-net/vsn-members/global-advisory-committee-on-vaccine-safety
  4. Phillips A, Patel C, Pillsbury A et al. Safety of human papillomavirus vaccines: an updated review. Drug Safety 2018;41:329-46
  5. Kosalaraksa P, Mehlsen J, Vesikari T et al. An open-label, randomized study of a 9-valent human papillomavirus vaccine given concomitantly with diphtheria, tetanus, pertussis and poliomyelitis vaccines to healthy adolescents 11-15 years of age. Pediatric Infectious Disease Journal 2015;34:627-34
  6. Olsson SE, Restrepo JA, Reina JC et al. Long-term immunogenicity, effectiveness, and safety of nine-valent human papillomavirus vaccine in girls and boys 9 to 15 years of age: interim analysis after 8 years of follow-up. Papillomavirus Research 2020 10:100203
  7. Dhingra MS, Peterson J, Hedrick J et al. Immunogenicity, safety and inter-lot consistency of a meningococcal conjugate vaccine (MenACYW-TT) in adolescents and adults: a Phase III randomized study. Vaccine 2020;38:5194-201
  8. Halperin SA, McNeil S, Langley J et al. Tolerability and antibody response in adolescents and adults revaccinated with tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine adsorbed (Tdap) 4–5 years after a previous dose. Vaccine 2011;29:8459-65
  9. Australian Government Department of Health and Aged Care: Therapeutic Goods Administration. Safety. Available from https://www.tga.gov.au/safety/safety
  10. Phillips A, Hickie M, Totterdell J et al. Adverse events following HPV vaccination: 11 years of surveillance in Australia. Vaccine 2020;38:6038-46