Guidance

COVID-19 vaccination and blood clotting

Updated 14 June 2021

The UK vaccination programme has been very successful with more than 34 million people vaccinated and more than 10,000 lives already saved. The rapid rollout has meant that we have been able to protect more people and we are starting to lift the restrictions on our population. This leaflet is designed to help you make an informed decision about vaccination.

What is the concern?

Recently there have been reports of an extremely rare but serious condition involving blood clots and unusual bleeding after AstraZeneca (AZ) vaccination. Some people with this condition have suffered life changing effects and some have died. These cases are being carefully reviewed but the risk factors for this condition are not yet clear.

Although this condition remains extremely rare there is a higher risk in people after the first dose of the AZ vaccine. To date and overall, just over 10 people develop this condition for every million doses of AZ vaccine given. This is seen more often in younger people and tends to occur between 4 days and 4 weeks following vaccination.

Similar conditions can also occur naturally, and clotting problems are a common complication of coronavirus (COVID-19) infection. An increased risk has not yet been seen after other COVID-19 vaccines in the UK.

Which vaccine will you be offered

Until recently we have relied upon all our vaccines being offered without preference to the whole population. The Joint Committee on Vaccination and Immunisation (JCVI) has considered the balance of risks and benefits and has now made the following advice (see table below for further information):

40 years of age and older or with underlying medical conditions

Older adults (including health and social care workers aged 40 years or older[footnote 1]), care home residents and adults of any age with certain medical conditions are at high risk of the complications of COVID-19.

The Medicines and Healthcare products Regulatory Agency (MHRA) and the JCVI advises that you should still receive any of the available COVID-19 vaccines [footnote 2]. The benefits of vaccination in protecting you against the serious consequences of COVID-19 outweigh any risk of this extremely rare condition.

If you are a healthy person aged 30 to 39 years of age

In the current situation the JCVI has advised that it is preferable for people in this age group to have a vaccine other than AZ. You are more at risk of the serious consequences of COVID-19 and will have the most benefit from being vaccinated if you are older, male, from certain minority ethnic backgrounds, in some occupations, or are obese.

It is important that you have the vaccination as soon as possible to protect you and to reduce the chance of passing on the virus. If the situation changes and you are offered the AZ vaccination you may go ahead after you have considered all the risks and benefits. Please carefully consider the risk to both you and your family and friends of COVID-19 before making your decision (please see table below).

If you are a healthy younger person aged 18 to 29

Currently JCVI has advised that it is preferable for people under 30 to have a vaccine other than AZ because the risk from COVID-19 infection is so low. If you are offered the AZ vaccination you may wish to go ahead after you have considered all the risks and benefits for you.

About the second dose

If you have already had a first dose of AZ vaccine without suffering this rare side effect you should complete the course. This includes people aged 18 to 39 years who are health and social care workers, unpaid carers and family members of those who are immunosuppressed. It is expected that the first dose of the vaccine will have given you some protection, particularly against severe disease.

Having the second dose will give you higher and longer lasting protection and tends to cause less of the common side effects (including short lived headache).

Benefits and risks of the vaccination

Age Risk from COVID-19 Risk of vaccination Benefit of vaccination
50 years of age or older or with underlying medical conditions Very high – hospitalisation, intensive care admission, death Uncommon – sore arm, feeling tired, headache, general aches, flu like symptoms 1 dose – more than 80% reduction: deaths, hospitalisation, intensive care
  Moderate – long COVID Extremely rare – clotting problems (around 1 in 100,000 first doses) 2 doses – more than 95% reduction: deaths
  Low – chance of catching and spreading infection    
40 to 49 years of age High – chance of catching and spreading infection Common – sore arm, feeling tired, headache, general aches, flu like symptoms 1 dose – more than 80% reduction: deaths, hospitalisation, intensive care
  Moderate – hospitalisation, intensive care admission, death, long COVID Extremely rare – clotting problems (around 1 in 100,000 first doses) 2 doses – more than 95% reduction: deaths
30 to 39 years of age High – chance of catching and spreading infection Common – sore arm, feeling tired, headache, general aches, flu like symptoms 1 dose – between 60% and 70% reduction: catching and passing on infection
  Moderate – long COVID Extremely rare – clotting problems (around 1 in 50,000 first doses) 2 doses – more than 85% reduction: catching and passing on infection
  Low – hospitalisation, intensive care admission, death    
18 to 29 years of age Very high – chance of catching and spreading infection Very common – sore arm, feeling tired, headache, general aches, flu like symptoms 1 dose – between 60% and 70% reduction: catching and passing on infection
  Moderate – long COVID Extremely rare – clotting problems (around 1 in 50,000 first doses) 2 doses – more than 85% reduction: catching and passing on infection
  Very low – hospitalisation, intensive care admission, death    

What to look out for after vaccination

Although serious side effects are very rare, if you experience any of the following from around 4 days to 4 weeks after vaccination you should seek medical advice urgently:

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

Further information can be found at NHS.UK.

  1. This includes unpaid carers and family members of those who are immunosuppressed. 

  2. If you have certain rare blood clotting disorders then you should discuss whether you can have the AZ vaccine with your specialist.