How do COVID-19 vaccines work?

Learn how vaccines train a person’s immune system and how the different types of COVID-19 vaccines work.

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COVID-19 vaccines – how vaccines work

This video describes how vaccines work in the body after you receive a vaccination.

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Safe, effective COVID-19 vaccines will offer protection against the virus, helping to prevent death and serious illness.

But how do they actually work?

Like other vaccines, such as the flu shot, COVID-19 vaccines will be given with a needle.

This triggers an immune response in the body – which is the body’s natural way of defending itself.

The vaccine will strengthen your immune system by training it to recognise and fight against the virus that causes COVID-19. Vaccines may contain either killed or weakened versions of the virus that causes the disease – or a small part of the virus, such as a protein.

There is no risk that you will get the disease from a vaccine.

When your immune system recognises this virus, or parts of it, in the vaccine as being foreign, it responds by creating memory cells and antibodies that will protect you against future infection or disease.

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

To learn more, visit health.gov.au

Vaccines train a person’s immune system to recognise and clear out germs (bacteria and viruses) that can cause serious illness. They strengthen your immune system by training it to recognise and fight against specific germs.

Vaccines are a safe way of producing an immune response in the body without causing illness.

Vaccines contain either killed or weakened versions of the virus that causes the disease or a small part of it, such as a protein or nucleic acid. When you get a vaccine, your immune system recognises these as foreign. It responds by creating memory cells and antibodies that protect you against future infection.

How will a vaccine prevent COVID-19?

The coronavirus that causes COVID-19 has spikes of protein on each viral particle. These spike proteins allow the virus to attach to cells and cause disease.

The vaccines in development help the body to “recognise” these spike proteins as foreign and fight the coronavirus that has them. The vaccine will protect a person who receives it by lowering their chances of getting COVID-19 if they encounter the coronavirus.

If you have already had COVID-19 and recovered, you may have some natural immunity to contracting the disease again. However because this virus is new, it’s not clear how long natural immunity might last.

Even if you have had COVID-19, you should still have the vaccine to help protect against getting COVID-19 again or passing it onto someone else.

Are COVID-19 vaccines effective?

The Therapeutic Goods Administration (TGA) will only approve a vaccine if it is effective. This means that any vaccine available in Australia has been proven to be effective in protecting against COVID-19.

Scientists will continue collecting evidence on the ongoing impact of vaccines.

How long does a COVID-19 vaccine last?

It is not yet known how long the protection afforded by a COVID-19 vaccine will last. This is being evaluated in ongoing research.

Will I need boosters?

Most COVID-19 vaccines require two doses. This includes the Vaxzevria (AstraZeneca) vaccine, the Comirnaty (Pfizer) vaccine and the Novavax vaccine. Whether you will need additional booster doses, such as an annual booster, for COVID-19 vaccines is still being determined by ongoing clinical trials.

Development and approval of COVID-19 vaccines

The TGA requires strong scientific data and analysis before approving a vaccine for use in Australia. The urgency of the global pandemic means that all available resources and efforts go towards developing and rolling out effective vaccines.

Clinical trials progress more quickly if a disease is widespread, as is the case with COVID-19 in many countries. This means researchers can test a vaccine much sooner than they could for a rare infectious disease.

Types of COVID-19 vaccines

There are many types of vaccines under development for COVID-19. The common aim is to cause an immune response that is specific to the COVID-19 coronavirus without making us sick.

Most COVID-19 vaccines use the coronavirus ‘spike’ protein to cause this immune response. Our immune system recognises this spike protein as foreign and produces long-lasting immune cells and antibodies.

If a vaccinated person is exposed to the coronavirus at a later time, their immune system will respond faster and more effectively.

Here are some of the common types, and how they work.

Messenger RNA (mRNA)

mRNA vaccines use a genetic code called RNA to spark the production of the coronavirus’ specific spike protein. Once the mRNA enters the body’s cells, the cells use the instructions contained in the RNA to make the spike protein. Immune cells then recognise the spike protein as foreign and begin building an immune response against it. The RNA from the vaccine does not change or interact with our DNA in any way. 

Protein

Protein based vaccines use a non-infectious component of the coronavirus, usually the spike protein. This protein is found on the surface of the virus and is manufactured in a laboratory. When the vaccine enters the body, immune cells recognise the spike protein as foreign. Immune cells then recognise the spike protein as foreign and begin building an immune response against it.

Vector

Vector vaccines use a harmless, weakened animal virus that contains the genetic code for a protein unique to the coronavirus, usually the spike protein. This weakened animal virus is known as a viral vector. Once this enters the body, it instructs our cells to make the coronavirus spike protein. Our cells use these instructions to make copies of the protein. Our immune cells then recognise the spike protein as foreign and begin building an immune response against it.

Find out more about COVID-19 vaccines and getting vaccinated in Australia.

National Coronavirus Helpline

If you need information about COVID-19, COVID-19 vaccines or help with the COVIDSafe app, call 1800 020 080. If you need assistance with booking a COVID-19 vaccine appointment, please note the call centre is unable to book appointments on your behalf. The line operates 24 hours a day, 7 days a week.

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Last updated: 
2 September 2021

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