Like all medicines, vaccines can cause side effects. Covid vaccines tap into our immune system’s natural response to an infection, which can make us feel temporarily unwell.

Most vaccine side effects are mild and short-term, and not everyone gets them.

  • Having a painful arm where you had your injection. This tends to be worst around 1-2 days after the vaccine
  • Feeling tired
  • Headache
  • General aches, or mild flu-like symptoms

Recently there have been reports of an extremely rare condition involving blood clots and unusual bleeding after the Oxford/AstraZeneca vaccine. Read more about the risk of blood clots in our helpful article.

If you experience any of the following from around four days to four weeks after vaccination you should seek medical advice urgently:

  • a severe headache that is not relieved with simple painkillers or is getting worse or feels worse when you lie down or bend over
  • an unusual headache that may be accompanied by blurred vision, confusion, difficulty with speech, weakness, drowsiness, or seizures (fits)
  • rash that looks like small pin prick bruises or bleeding under the skin beyond the injection site
  • shortness of breath, chest pain, leg swelling, leg pain or persistent abdominal (tummy) pain

Worldwide, there have also been recent, rare cases of inflammation of the heart called myocarditis or pericarditis reported after Covid vaccines, although it is not yet clear that these are caused by the vaccines. These cases have been seen mostly in younger men within several days after vaccination.

You should seek medical advice urgently if you experience:

  • chest pain
  • shortness of breath
  • feelings of having a fast-beating, fluttering, or pounding heart

There is no evidence that Covid vaccines have any effect on fertility or your chances of becoming pregnant and there is no need to avoid pregnancy after Covid vaccination.


This content has been reviewed by clinicians and public health professionals Page last reviewed: 11 August, 2021