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Vaccine side effects and safety

Millions of people have had a coronavirus (COVID-19) vaccine and the safety of the vaccines continues to be monitored. Reports of serious side effects are very rare.

Common side effects

Very common side effects in the first day or two include:

  • having a painful, heavy feeling and tenderness in the arm where you had your injection
  • feeling tired
  • a headache
  • feeling achy and chills
  • feeling or being sick

You may also have flu like symptoms with a high temperature or episodes of shivering and shaking for a day or two.

However, a high temperature could also indicate that you have COVID-19 or another infection (see ‘what should I do if I’m concerned about my symptoms’). You can rest and take the normal dose of paracetamol (follow the advice in the packaging) to help make you feel better.

You cannot catch COVID-19 from the vaccine, but you may have caught it just before or after your vaccination.

More information can be found on what to expect after your COVID-19 vaccination.

Report a side effect using the COVID-19 Yellow Card website.

Very rare side effects

Allergic reactions

Most people with allergies (including food or penicillin allergies) can be vaccinated against COVID-19.

Tell healthcare staff before you're vaccinated if you've ever had a serious allergic reaction (including anaphylaxis). They may ask what you're allergic to, to make sure you can have the vaccine.

Serious allergic reactions to the COVID-19 vaccines are very rare.

If you do have a reaction, it usually happens in minutes. Staff giving the vaccine are trained to deal with allergic reactions and treat them immediately.

If you have a serious allergic reaction to the 1st dose of a vaccine, you should not have the same vaccine for your 2nd dose.

Blood clotting

The JCVI has weighed the relative balance of benefits and risks and has advised that the benefits of prompt vaccination with the AstraZeneca COVID-19 vaccine far outweigh the risk of adverse events for individuals 40 years of age and over and those who have underlying health conditions which put them at higher risk of severe COVID-19 disease.

The JCVI currently advises that it is preferable for adults aged under 40 years who are healthy and without underlying health conditions that put them at higher risk of severe COVID-19 disease, to be offered an alternative COVID-19 vaccine, if available.

It is your option to make an informed choice to receive the AstraZeneca COVID-19 vaccine if you wish to receive earlier protection.

Find out more about COVID-19 vaccination and blood clotting.

Find out more about COVID-19 vaccination and myocarditis and pericarditis.

Heart inflammation

There have been rare cases of inflammation of the heart reported after COVID-19 vaccination. Most people who had this recovered following rest and simple treatments.
It is not yet clear if it was caused by the vaccines, but get urgent medical advice if you have any of these symptoms within a few days of being vaccinated:

  • chest pain
  • shortness of breath
  • a fast-beating, fluttering or pounding heart (palpitations)

Menstrual disturbance

The Medicines and Healthcare products Regulatory Agency (MHRA) is closely monitoring reports of menstrual disorders (period problems) and unexpected vaginal bleeding following vaccination against COVID-19 in the UK. These reports have also been reviewed by the independent experts of the Commission on Human Medicines’, COVID-19 Vaccines Benefit Risk Expert Working Group and members of the Medicines for Women’s Health Expert Advisory Group.

The current evidence does not suggest an increased risk of either menstrual disorders or unexpected vaginal bleeding following the vaccines.

A range of menstrual disorders have been reported after all three of the COVID-19 vaccines including heavier than usual periods, delayed periods and unexpected vaginal bleeding. The number of reports of menstrual disorders and vaginal bleeding is low in relation to both the number of females who have received COVID-19 vaccines to date and how common menstrual disorders are generally. The MHRA will continue to closely monitor reports of menstrual disorders and vaginal bleeding with COVID-19 vaccines.

How COVID-19 vaccines are developed, tested and approved

COVID-19 vaccines have to go through several stages of clinical trials before they can be approved for use.

Clinical trials are where a vaccine or medicine is tested on volunteers to make sure it works and is safe.

The approved COVID-19 vaccines have been tested on thousands of people in the UK and around the world, including:

  • people from different ethnic backgrounds
  • people aged between 18 and 84
  • children and young people aged between 12 and 17
  • people with different health conditions

All vaccines used in the UK must be approved by the independent Medicines and Healthcare products Regulatory Agency (MHRA).

The MHRA makes sure the vaccines meet strict international standards for safety, quality and effectiveness. Once a vaccine is approved, it's closely monitored to continue to make sure it is safe and effective.