How vaccines are developed
It can take many years to develop and gain approval for a new vaccine. Vaccines go through many phases of development:
- pre-clinical testing
- clinical testing
- regulatory approval.
Sometimes, increased resources and funding, and concurrent clinical trials can fast-track development, such as with COVID-19 vaccines.
Every vaccine in Australia must pass 3 trial phases before the Therapeutic Goods Administration (TGA) registers it for use.
Phase 1 trials
The new vaccine is given to a small number of healthy adults to assess safety.
Phase 2 trials
If the new vaccine is found safe, it is given to hundreds of people to test:
- how effectively it stimulates immune responses
- how much or how many doses need to be given to protect against the target disease
- whether there are any side effects.
Phase 3 trials
If the vaccine is found safe and effective, it is given to thousands of people to test:
- if it protects large populations from the target disease
- if there are any uncommon or serious side effects.
Vaccine safety monitoring
Vaccines are like other medicines and can have side effects. However, all vaccines used in Australia provide benefits that greatly outweigh their risks.
All vaccines must be rigorously assessed by the TGA and meet high standards before they can be registered and approved for use in Australia.
This includes analysis of:
- clinical trial data
The TGA also assesses the quality of every batch of vaccine before it can be supplied in Australia.
After vaccines are given to people, their safety continues to be monitored using passive or active surveillance.
Passive surveillance requires people to report side effects to the TGA.
Consumers, health professionals, the companies who supply vaccines, and state and territory health departments can report side effects or adverse events to the TGA.
Active surveillance is done using a system called AusVaxSafety. Participating vaccination clinics send short SMS messages to people after they received vaccines (or their parents or carers) to ask if they had any reactions. Independent experts analyse the responses to make sure that any safety issues are detected quickly.
Read more about active surveillance on the AusVaxSafety website.
AusVaxSafety is a national system monitoring vaccine safety in Australia. The report shows how people receiving vaccines, or their parents and carers, responded to the SMS about their health a few days after vaccination at each schedule point in the National Immunisation Program in Australia 2020.
Vaccine ingredients vary depending on what the vaccine is for. They may contain:
- a very small dose of a live (but weakened) virus
- killed viruses
- killed bacteria
- small parts of bacteria
- a small dose of a modified toxin produced by bacteria
- a small amount of preservative
- a small amount of an antibiotic to preserve the vaccine
Each vaccine component serves a specific purpose, and each ingredient is tested for safety in the manufacturing process.
The TGA considers the safety, quality and efficacy of every ingredient in a vaccine before they register the vaccine for use in Australia.
No vaccine used in Australia contains mercury (thiomersal).
Find out more about TGA's Product Information (Provides vaccine specific ingredients)
Vaccine side effects
You are more likely to experience a serious complication from a disease, rather than from the vaccine for that disease.
It is not uncommon to experience minor side effects after a vaccination, such as pain and redness at the injection site. Most side effects only last a couple of days and you will recover without any problems.
Most common side effects are a sign that your body is starting to build immunity (protection) against a disease.
Serious side effects from vaccines are extremely rare. If you have questions or concerns about a reaction to a vaccine, talk with your healthcare provider.
Learn more about possible side effects of vaccination
Some adverse events coincide with, but are not caused by vaccination
Studies have shown that many common symptoms are not always caused by the vaccine but occur at the same time by chance.
Symptoms such as fever, rashes, irritability are common, especially among children.
It can be difficult to determine how many of these reactions are caused by a vaccine when the ‘background rate’ (how often it occurs anyway) in the same age group is unknown.
Medical conditions with unknown causes have been incorrectly linked to particular vaccines. The most prominent example is the claimed link between the measles–mumps–rubella (MMR) vaccine and autism.
There is no established link between vaccines and autism. The MMR vaccine doesn’t cause autism. Many studies and reviews over almost 20 years have found no link between the MMR vaccine and autism.
It’s normal to have questions about vaccination. Misinformation on the internet and social media about the safety of vaccines has also caused concern for some people.
Learn more about vaccines and safety.
Find more information:
- The Science of Immunisation: Questions and Answers
- Sharing Knowledge About Immunisation website
- MumBubVax website
- National Centre for Immunisation Research and Surveillance