Immunity - AstraZeneca COVID-19 vaccine

Vaccines teach your immune system (your body's natural defences) how to protect you from diseases.

It is much safer for your immune system to learn how to protect you from COVID-19 through vaccination than by catching the virus.

We do not know yet how long immunity will last. Clinical trials are ongoing to find this out.

The official name of AstraZeneca's COVID-19 vaccine is 'Vaxzevria'. But most people call it 'AstraZeneca'.

How long it takes to work

You will need 2 doses of the AstraZeneca COVID-19 vaccine.

After having both doses, most people will have immunity. This means you will be protected against COVID-19.

It takes 15 days after getting the second dose to have the best protection.

Getting your second dose

You should attend your appointment for your second dose when invited.

This will be 4 to 12 weeks after your first dose.

If you take immunosuppressive medicines

If you have a weakened immune system, your COVID-19 vaccine may not work as well for you. But there is no extra risk in getting it.

Read more about weak immune systems and COVID-19

Testing and evidence

Worldwide, vaccines save at least 2 to 3 million lives each year. They protect many more from lifelong illnesses.

Millions of people have now received COVID-19 vaccines all over the world. 

There’s strong, reliable evidence that COVID-19 vaccines greatly reduce your risk of getting COVID-19. They’re highly effective at preventing deaths and serious illness with COVID-19.

Protection from COVID-19

There is a small chance you might still get COVID-19 after vaccination. Even if you do get COVID-19, being vaccinated can reduce how serious your symptoms will be.

There is some new evidence to show that the vaccines may reduce you spreading COVID-19 to other people but more research is needed.

The HSE, Department of Health and the World Health Organization recommends that you get your COVID-19 vaccine when it is offered to you.

Even after you are vaccinated, continue to follow public health advice on how to stop the spread of COVID-19. For example, social distancing, wearing a face covering and washing your hands properly and often.

Read more about how you can protect yourself from COVID-19


This content was fact checked by vaccine experts working in Ireland.

Last updated: 29 July 2021 at 3pm

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