About vaccines

Vaccines are medicines that help to protect you and your family from infectious diseases.

We need vaccines because some infectious diseases can make people very sick. They can even kill people.

Vaccines also stop infectious diseases spreading in the community.

Vaccines build your body’s immune system. This helps your body to defend itself against the viruses and bacteria that cause infectious diseases.

Effectiveness, safety and quality: the aims of vaccine development

Vaccines are approved for use only if they have been shown to be effective, safe and high quality.

Effectiveness
Effectiveness means the vaccine works. A vaccine that works is one that reduces the number of people who get sick from an infectious disease.

To be approved for use, all vaccines must work, but they might work better in some groups of people than others. For example, vaccines tend to be less effective in older people.

Safety
Safety means that a vaccine doesn’t harm people in unexpected and serious ways.

A vaccine can be safe and still have side effects. Many vaccines have common side effects like fever or pain and redness where the vaccine is injected. Serious side effects from vaccines are extremely rare.

Quality
Quality means that the vaccine has the ingredients it’s supposed to have and only those ingredients. It also means that every batch of vaccine is manufactured the same way as all other batches, and the manufacturing process is closely supervised.

In Australia the Therapeutic Goods Administration (TGA) approves medicines for use. It approves medicines only after checking with experts that the medicines meet strict standards for effectiveness, safety and quality. And once the TGA approves medicines and people start using them, the TGA keeps monitoring the medicines to make sure they’re working the way they’re supposed to and are still safe.

How vaccines are developed

Like all medicines, vaccines go through extensive research and testing before the TGA and regulation agencies in other countries approve them for use. This ensures that vaccines are effective, safe and high quality.

The vaccine development process is the same as the process for other medicines. It has 2 main stages.

Stage 1: research, development and laboratory testing
In this stage, laboratory researchers study the virus or bacteria that causes the infectious disease.

When the researchers understand how the virus or bacteria causes disease, they can work out how to stop it. They come up with experimental vaccine products that they think will stop the virus or bacteria. These products might be dead or weakened viruses or bacteria, viral or bacterial genetic code, and so on.

Animal testing also happens in this stage. Researchers test their products on animals to see how the vaccines might work in humans. These tests also give researchers an idea of whether the products are likely to be safe for humans.

When researchers think their experimental products are likely to work and be safe, the development process moves on to stage 2.

Stage 2: human clinical trials
Clinical trials have 3 phases. These phases take place out of the laboratory and in settings like hospitals. People participating in trials are closely monitored.

In phase I, expert investigators give the vaccine to 25-50 young, healthy adults. This phase aims to show that the vaccine is safe.

In phase II, investigators give the vaccine to hundreds of people, including people like those who’ll eventually use the vaccine – for example, people of the same age and physical health. This phase aims to:

• see whether the vaccine reduces the number of people who get sick
• work out the best dose
• see whether there are any side effects.

If the vaccine is found to be safe and effective, it moves to phase III.

In phase III, investigators give the vaccine to thousands of people. This phase aims to:

• see whether the vaccine protects large populations from the infectious disease, including some special-risk groups
• find any uncommon or serious side effects.

CIinical trial rules
Clinical trials must follow very strict rules. These rules ensure that the trials produce reliable evidence about the vaccines.

For example, there are rules about what to do if people get sick or have unusual or unexpected reactions to vaccines during clinical trials. If this happens, the clinical trial must stop while investigators work out why the reaction happened and whether this poses a safety risk. The trial can start again only when investigators and independent safety experts are sure that the vaccine is safe.

Vaccine development involves many people and organisations. They include scientists, volunteers, universities, research facilities, biotechnology companies and pharmaceutical companies.

How long does vaccine development take?

Vaccines usually take a very long time to develop – often up to 10 years.

This is because it can take a long time to:

• get funding for initial research on diseases and experimental vaccine products
• organise expert investigators to run clinical trials
• organise people to take part in clinical trials
• get enough information in each stage or phase so the process can move on.

After a vaccine is developed: approval, roll-out and manufacturing

Approval
If the vaccine successfully passes through all phases of clinical trials, it can be submitted to the TGA for approval. If the TGA approves it, it can be used in Australia.

Roll-out
Once the TGA approves a vaccine, independent experts advise the Australian Minister for Health on how to roll out the vaccine. For example, they consider:

• whether the vaccine should be included in the National Immunisation Program Schedule or rolled out as part of a mass vaccination program
• who should get the vaccine first
• how to manage practical roll-out issues, like storage, distribution and vaccination.

Manufacturing
The manufacturing process for vaccines is complex because vaccines must be produced to strict quality standards. Also, they often need to be stored and distributed in special conditions to ensure their safety and effectiveness.

And every batch of vaccine that’s manufactured must be checked for quality before it’s sent out for use.

For more information on Australia’s mass vaccination program for COVID-19, go to Australian Government Department of Health – COVID-19 vaccines.

After a vaccine has been rolled out: monitoring

Once a vaccine is on the market and being used, the TGA monitors the vaccine for overall safety. It watches for any rare and serious side effects. Sometimes side effects are so rare that they don’t come up in clinical trials.

Monitoring happens in a couple of ways:

• Investigators might do phase IV clinical trials. These are further studies on vaccine effectiveness and side effects in real-world settings over longer periods of time.
• The TGA has reporting systems that keep track of how the vaccine is working in the community.

If the TGA thinks there’s a problem with a vaccine, it checks the problem thoroughly and takes action to manage risks. This action might include:

• setting up extra monitoring
• putting alerts about side effects on vaccine packaging
• limiting the groups of people that get the vaccine
• recalling particular batches of the vaccine
• withdrawing the vaccine from use.

COVID-19 vaccine development

COVID-19 vaccine development has happened faster than usual. This is because COVID-19 has caused a global pandemic. We have urgently needed COVID-19 vaccines to protect people’s health, stop people dying, and limit the social and economic effects of the virus.

Governments, research organisations and pharmaceutical companies have worked together to speed up the process in the following ways:

• People and organisations have invested much more money than usual in the development process. This extra money has meant that more people have been able to do more work and use more resources to develop vaccines.
• Some of the clinical trial phases have happened at the same time. Usually the phases happen one after the other.
• There have been a lot of COVID-19 cases in the community. This has made it easier for scientists to assess whether the vaccines are working.
• More people have been willing to take part in clinical trials.
• Scientists worked out the virus’s genetic sequence early on in the pandemic, and they shared this information with other scientists. This meant that the early stages of vaccine development started very quickly.

The COVID-19 vaccines that are approved for use in Australia have successfully passed through all clinical trial phases and met all safety, effectiveness and quality standards. The TGA is continually checking that they are safe and working as they should for people across the world.