About the COVID-19 Vaccine

Following a review of the use of the COVID-19 AstraZeneca vaccine, the Australian Technical Advisory Group on Immunisation (ATAGI) recommends that the COVID-19 vaccine by Pfizer is preferred over the COVID-19 vaccine by AstraZeneca in adults aged under 50 years. Find out more.

How do the COVID-19 vaccines work?

The COVID-19 vaccines work by preparing the body to defend itself against COVID-19.

When a person is given the Pfizer/BioNTech COVID-19 vaccine, some of their cells will read the vaccine’s mRNA instructions and temporarily produce the spike protein, which mimics the COVID-19 virus. The person’s immune system will then recognise this protein as foreign and produce antibodies and activate T cells (white blood cells) to attack it.

When a person is given the AstraZeneca COVID-19 vaccine, some of their cells will be “infected” by a dead adenovirus (common cold) carrying the DNA for the spike protein, which mimics the COVID-19 virus. The person’s immune system will then recognise this protein as foreign and produce antibodies and activate T cells (white blood cells) to attack it.

Once vaccinated, if a person comes into contact with COVID-19, their immune system will recognise it and be ready to defend the body against it having already been exposed to the vaccine.

As a result, you will be less likely to have severe COVID-19 symptoms after a vaccination.

How do the COVID-19 vaccines protect me?

The goal of vaccination is to stop you from getting sick.

The COVID-19 vaccines train your immune system to recognise COVID-19. They have been designed to help you fight off COVID-19 before it makes you sick, and to reduce the severity of your symptoms if you do get sick.

Most vaccines work in this way. This is why it’s so important that everyone gets vaccinated.

During clinical trials of the COVID-19 vaccines, research focussed on whether the vaccines helped produce enough antibodies to stop us from getting sick. The ones that did this safely and effectively have been approved for use.

Now that the vaccines are being rolled out world-wide, early research suggests they may also be able to reduce how infectious we are if we do catch COVID-19, which could help stop or reduce the spread of the virus.

It is very important that we continue practising good hygiene, using the COVID Safe Check In, physical distancing, and getting tested and staying home if you are unwell, especially during the roll out of the vaccination program.

What’s in the COVID-19 vaccines?

Vaccine ingredients vary depending on what the vaccine is for. Generally, vaccines may contain some of the following ingredients:

  • a protein component of a virus
  • a piece of genetic code (DNA or mRNA)
  • a very small dose of a weakened virus
  • a substance to boost the immune response (an adjuvant)
  • a small amount of preservative
  • sterile salt water (saline) for injections

Ingredients for the COVID-19 vaccines approved for use in Australia will be listed in the Australian Register of Therapeutic Goods.

Do the vaccines contain any animal products?

The approved COVID-19 vaccines do not contain any animal products or egg.

Can the vaccine give me COVID-19?

No, the COVID-19 vaccines available do not use the live or whole virus that causes COVID-19.

If I catch COVID-19 after I have the vaccine, can I pass the infection onto others?

Early research indicates that the vaccines may be able to reduce how infectious we are if we do catch COVID-19. The Therapeutic Goods Administration (TGA) will continue to monitor the ongoing research to understand whether the vaccines can stop a person passing the virus onto another person.

This is why it’s important that even if you have been vaccinated, you should continue practising good hygiene, using the COVID Safe Check-In, physical distancing, and getting tested and staying home if you are unwell.

Do I still need to practice hand hygiene and physical distancing even if I've been vaccinated?

It is very important that we continue practising good hygiene, using the COVID Safe Check-In, physical distancing, and getting tested and staying home if you are unwell, especially during the roll out of the vaccine program, which will take several months.

Australia will still need to have the flexible strategies already in place to control COVID-19. If the vaccine program is effective and results in a high proportion of people being vaccinated, it is hoped that we will be able to reduce some of these control measures. This is likely to be a slow process and will rely on many people being willing to have the vaccine.

How long does the vaccine protect me from getting COVID-19?

Clinical trials have shown that the COVID-19 vaccines protect against COVID-19 symptoms and severe disease after a person receives two doses. At this stage, there is not enough information to understand the long term protection against COVID-19 after vaccination. Booster doses may be required, similar to other vaccinations, such as the flu vaccine.

The Therapeutic Goods Administration (TGA) will continue to monitor the ongoing research to understand how the vaccines work over time. This is why it’s important that even if you have been vaccinated, you should continue practising good hygiene, using the COVID Safe Check-In, physical distancing, and getting tested and staying home if you are unwell.

Are there any side effects?

Vaccines, like any other medication or natural therapy, can have reactions or side effects. The extent and severity of side effects of the COVID-19 vaccines are similar to those from other vaccines. As part of regulatory assessment of all vaccines, the Therapeutic Goods Administration (TGA) considers information about possible side effects. For a vaccine to be registered for use in Australia, the benefits must outweigh the risks.

You may experience minor reactions or side effects following vaccination. Most reactions or side effects last no more than a couple of days and do not require special treatment. Serious reactions like allergic reactions are extremely rare.

Vaccines are monitored for a long time and even after a vaccine is given, it is still monitored for safety. Healthcare professionals contribute to ongoing monitoring by informing the TGA of any side effects, even if they are very minor. This means the TGA can oversee the safety of a vaccine across the country and, in the unlikely event that there is a safety risk, inform healthcare providers, the community and the Government as soon as possible.

Common reactions to the COVID-19 vaccine include:

  • tenderness, pain and swelling at the injection site
  • tiredness
  • headache
  • muscle and joint pain
  • chills
  • fever.

Some people may also experience redness at the injection site, nausea, itching at the injection site, pain in the limb, enlarged lymph nodes, difficulty sleeping or generally feel unwell.

Why do vaccines cause reactions or side effects?

Reactions or side effects, such as fever and tiredness, from vaccines are often a really good sign that your immune system has been activated and is learning how to fight the disease you’ve been vaccinated against.

Do the COVID-19 vaccines work on new variants?

It is anticipated that the COVID-19 vaccines will be effective against the newer strains of COVID-19.

This is because the vaccines work by inducing what is known as a "polyclonal" response – a collection of immunological responses to many different parts of the COVID-19 "spike" protein. In the new variants, only a limited part of the spike protein is changed, and much is unchanged, so the vaccines should still work against the main, unchanged parts to the COVID-19 spike protein.

The Australian Government will continue to closely monitor developments and do their own genetic examination of any local cases.