COVID-19 vaccine side effects: Your questions answered

22nd March, 2021 • 5 min read
Reviewed by

Several COVID-19 vaccines are now in use and they’re already saving lives. But if you haven’t had a vaccine yet, you might be worried about the possible side effects.

So read on to learn the facts, including what the common COVID-19 vaccine side effects are, why they’re usually nothing to worry about and when to get medical advice.

Common side effects

COVID-19 vaccines by Pfizer/BioNTech, Oxford/AstraZeneca and Moderna have now been approved for use in many countries around the globe. These have been thoroughly tested for both safety and effectiveness.

As with any medicine, however, vaccines can cause side effects. These are usually mild and not everyone gets them.

Common side effects are thought to affect more than 1 in 10 people. For the Pfizer/BioNTech, Oxford/AstraZeneca and Moderna COVID-19 vaccines, the most common side effects include:

  • pain or soreness in the arm where you had the injection
  • tiredness
  • headache
  • muscle aches and joint pains
  • fever
  • chills
  • feeling or being sick

In addition, the Moderna COVID-19 vaccine can also commonly cause:

  • tenderness and swelling of the underarm on the side you had the injection
  • a rash, redness or hives where you had the injection

Less common side effects

Most people will only get mild side effects from the COVID-19 vaccines. Some other side effects have also been reported, but these are much less common. They include:

  • itchiness at the injection site
  • severe allergic reaction (anaphylaxis) – very rare side effect of all 3 vaccines
  • temporary drooping of the face on one side (Bell’s palsy) – has been observed with the Pfizer/BioNTech and Moderna vaccines but more research is needed to tell if it is related to the vaccine or not
  • facial swelling – rare side effect of the Moderna vaccine

The European Medicines Agency (EMA) has said that unusual blood clots combined with low blood platelets should be listed as a very rare side effect of the Oxford/AstraZeneca vaccine. You can read more about this


When to get emergency medical help

Serious side effects from the COVID-19 vaccines are rare, but there have been reports of severe allergic reactions.

If you've ever had a bad allergic reaction in the past, you should tell medical staff before you have a COVID-19 vaccine.

If you do have a bad allergic reaction to the vaccine, it will usually happen very quickly – within a few minutes of having the injection – so there will be people on hand who are trained to deal with it.

After having a vaccine, if you notice any symptoms of an allergic reaction – such as swelling of your face or tongue, an itchy rash or shortness of breath – seek emergency medical help.

If you develop any of the following symptoms 4 days to 4 weeks after being vaccinated against COVID-19, you should get medical help urgently:

  • new onset of severe headache, which is getting worse and does not respond to simple painkillers
  • an unusual headache which seems worse when lying down or bending over, or may be accompanied by blurred vision, nausea and vomiting, difficulty with speech, weakness, drowsiness or seizures
  • new unexplained pinprick bruising or bleeding
  • shortness of breath, chest pain, leg swelling or persistent abdominal pain

When to speak to a doctor

If you’re worried about any side effects or symptoms after having a COVID-19 vaccine, speak to a healthcare provider for advice. You should let them know you’ve had a vaccine.

Treating side effects at home

If you do get mild side effects after having a COVID-19 vaccine, you should be able to manage them at home.

Try to rest as much as possible. You can take common painkillers to help with symptoms such as headache and fever – just make sure they're suitable for you and follow the instructions on the packaging.

How long do the side effects last?

Mild side effects are normal, and a sign that your body’s immune system is responding to the vaccine and learning how to fight the virus. They usually go away within a few days and shouldn't last longer than a week.

Is it ‘good’ to get side effects?

While side effects are common, it's also fine not to get any. It doesn’t mean the vaccine isn’t working – your immune system is just responding more quietly.

Are there any long-term side effects?

During clinical trials for a vaccine, any side effects are thoroughly investigated and play a huge part in whether or not a vaccine gets approved. What's more, since the roll-out of the COVID-19 vaccines at the end of last year, in many countries around the world, no other safety concerns have been identified so far.

However as with all vaccines, the COVID-19 vaccines are constantly being monitored, and any possible risks remain under review. Research on COVID-19 vaccines is moving quickly and we’re learning more every day.

Key points

  • all the approved COVID-19 vaccines have been thoroughly tested for safety and effectiveness
  • it’s common to get some mild side effects after having a COVID-19 vaccine
  • common side effects include a sore arm, tiredness, headache, fever, aches and chills
  • these usually go away within a day or 2 and don’t last for more than a week
  • contact your doctor if you’re worried about any side effects or feel unwell for more than a week
  • seek emergency medical care if you think you’re having an allergic reaction to a vaccine

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.