Immunity - Pfizer/BioNTech COVID-19 vaccine

Vaccines teach your immune system 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.

How long it takes to work

It takes 7 days after the second dose for the Pfizer/BioNTech COVID-19 vaccine to work. This is when you are fully vaccinated.

You should get your second dose 21 to 28 days after your first dose.

Protection from COVID-19

After having both doses of a COVID-19 vaccine, most people will be protected against the virus.

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

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

COVID-19 vaccine testing and evidence

Worldwide, vaccines save at least 2 to 3 million lives each year, and protect many more from lifelong illnesses. Millions of people have now received COVID-19 vaccines all over the world. 

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


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

Last updated: 26 July 2021 at 5pm

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