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22nd December, 20205 min read

What to expect after having the COVID-19 vaccine

What to expect after having the COVID-19 vaccine
Medical reviewer: Dr Ann Nainan
Author: Kathryn Reilly
Last reviewed: 21/12/2020
Medically reviewed

All of Healthily's articles undergo medical safety checks to verify that the information is medically safe. View more details in our editorial policy

In the UK and the US, people have started to be vaccinated against COVID-19, receiving a vaccine made by the companies Pfizer and BioNTech. India, meanwhile, is in the process of testing a number of candidate vaccines.

But it’s understandable if you have questions about whether the vaccine is right for you. Read on to learn the facts about the Pfizer/BioNTech vaccine, including how safe it is, if everyone can have it, and the side effects you might get after you have it.

Is the Pfizer/BioNTech vaccine safe?

Vaccines are the best way to stop infections like COVID-19 – we already have effective vaccines for other illnesses, such as measles and the flu. And all vaccines go through a strict testing process before they’re approved for use, to make sure they’re safe.

However, you may have seen things about the vaccine that have worried you, on social media or other information sources. There are three common claims you may have seen about the Pfizer/BioNTech COVID-19 vaccine – but they’re not true.

First, it can’t give you COVID-19. This is because it doesn’t contain any live virus.

Second, it can’t change your genes. It uses a piece of genetic code, called mRNA, to teach your body’s defences (immune system) to fight the virus but there’s no way it could affect your genes.

And third, if you’ve already had COVID-19, this doesn’t mean you don’t need to have the vaccine. This is because we don’t know how long immunity lasts, so you could still get the virus again.
Covid-19 Coronavirus Vaccine vials in a row macro close up

Are there people who shouldn’t get the Pfizer/BioNTech vaccine?

While the Pfizer/BioNTech vaccine is safe for most people, there are some people it might not be suitable for. You should speak to your doctor if you:

  • have allergies
  • have a fever
  • have a bleeding disorder or are on a blood thinner
  • are immunocompromised or are on a medicine that affects your immune system
  • have received another COVID-19 vaccine

You shouldn’t get the Pfizer/BioNTech vaccine if you:

  • had a bad allergic reaction after a previous dose
  • have had a bad allergic reaction to any ingredient in the vaccine
  • are pregnant or are breastfeeding, or you plan to become pregnant (the vaccine hasn’t been tested on pregnant or breastfeeding women)

What are the side effects of the Pfizer/BioNTech vaccine?

Like all medicines, vaccines can cause side effects. Professor Peter Openshaw, a professor of experimental medicine at Imperial College London, says: “As with all food and medications, there is a very small chance of an allergic reaction to any vaccine. However, it is important that we put this risk in perspective.”

During the Pfizer/BioNTech tests, only a very small number of people had bad side effects: just 0.6% of people given the vaccine had a serious adverse reaction.

Not everyone gets any side effects at all, but if you do, they will probably be mild, and should ease or go away within a few days.

Common side effects include:

  • pain or tenderness in the arm where you had the injection
  • tiredness
  • headache
  • general aches, or mild flu-like symptoms
  • muscle pain
  • chills
  • joint pain
  • fever
  • injection site swelling
  • injection site redness
  • nausea
  • feeling unwell
  • swollen lymph nodes (lymphadenopathy)

If you do have mild side effects after the first dose of the vaccine, it’s important that you still have the second dose. This is because although the first dose gives some protection against the virus, the second dose will give you the best protection.

In a very few cases, people have had an allergic reaction to the vaccine. This is most likely to happen within a few minutes to an hour of being vaccinated. If you think you’re having an allergic reaction, call for urgent medical help.

If you get any side effects after having the vaccine, you can report them to your country's medicines reporting service – this will help everyone to learn more about the vaccine. In the UK, you can report side effects through the MHRA's Yellow Card scheme. In the US, use the FDA/CDC Vaccine Adverse Event Reporting System (VAERS).

Because this is a new vaccine, more side effects may be discovered over time, but it has had all the necessary and important safety checks.

Side Effects Infographic-Healthily

Can I stop wearing a mask when I’ve had the vaccine?

There are still many things that aren’t known about COVID-19, and we’re learning about the virus all the time. This means it’s important to follow the guidelines, even if you’ve had a vaccine. So, you should continue to wear a mask in public, stay 2 metres apart from people you don’t live with, and wash your hands regularly.
Woman on the street wearing a facemask

Key points

  • the Pfizer/BioNTech COVID-19 vaccine appears to be safe for most people
  • there are a few groups of people it might not be suitable for
  • most side effects are mild, and only last a few days
  • you must have both doses of the vaccine to get full protection
  • severe side effects are very rare

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COVID-19 and Your Health [Internet]. Centers for Disease Control and Prevention. 2020 [cited 21 December 2020]. Available here

COVID-19 vaccination: a guide for women of childbearing age, pregnant, planning a pregnancy or breastfeeding [Internet]. GOV.UK. 2020 [cited 17 December 2020]. Available here

COVID-19 vaccination: guide for older adults [Internet]. GOV.UK. 2020 [cited 17 December 2020]. Available here

COVID-19 Virtual Press conference [Internet]. 2020 [cited 17 December 2020]. Available here

Expert reaction to phase 3 results for the Pfizer/ BioNTech BNT162b2 mRNA COVID-19 Vaccine | Science Media Centre [Internet]. Science Media 2020 [cited 17 December 2020]. Available here

Expert reaction to reports of allergic reaction in two healthcare workers who had a history of serious allergies and who received the Pfizer COVID-19 vaccine | Science Media Centre [Internet]. Science Media 2020 [cited 17 December 2020]. Available [here](

User S. Vaccine information, ICMR New delhi - COVID-19 Vaccine [Internet]. 2020 [cited 22 December 2020]. Available here

About the vaccine used to protect against coronavirus (COVID-19) [Internet]. 2020 [cited 21 December 2020]. Available here

Blood Cancer UK | The coronavirus vaccine: what you need to know [Internet]. Blood Cancer UK. 2020 [cited 21 December 2020]. Available here

[Internet]. 2020 [cited 21 December 2020]. Available here

Information for UK recipients on Pfizer/BioNTech COVID-19 vaccine [Internet]. GOV.UK. 2020 [cited 21 December 2020]. Available here

Why vaccination is safe and important [Internet]. 2020 [cited 21 December 2020]. Available here

Pfizer-BioNTech COVID-19 Vaccine [Internet]. U.S. Food and Drug Administration. 2020 [cited 22 December 2020]. Available here

Coronavirus (COVID-19) vaccine [Internet]. 2020 [cited 22 December 2020]. Available here

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Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.

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