Frequently asked questions

What is my risk of getting a clot after the vaccine?

The data so far suggests that the risk of clot is an extremely rare adverse event associated with low platelets (a type of blood cell)  after vaccination with the Oxford/AstraZeneca vaccine. This is usually experienced between day 4-28 after vaccination.

Up to 5 May 2021, there were a total  of 262 cases (149 women and 112 men), with 51 deaths. Eight cases have been reported after a second dose. This was out of 23.3 million first doses, and 7.5 million second doses given.

These extremely rare blood clots can occur naturally in people that have not had the vaccine and in people with COVID-19.


How will I know if I have a clot?

Clots linked to the Oxford/AstraZeneca vaccine have been experienced between days 4-28 after vaccination. Some of the signs may include:

  • A new, severe headache which is not helped by usual pain relief or is getting worse
  • A headache that is worse when lying down or bending over
  • A headache with blurred vision, nausea and vomiting, difficulty with speech, weakness, drowsiness, or seizures
  • New, unexplained bruising or bleeding
  • Shortness of breath
  • Chest pain
  • Leg swelling
  • Persistent abdominal pain


I have a family history of blood clot, does this put me at increased risk?

Unless you have a personal history of one of the following listed conditions, you can proceed with the 2nd vaccination with Astra Zeneca

  • a history of cerebral venous sinus thrombosis -acquired or hereditary thrombophilia
  • heparin-induced thrombocytopenia and thrombosis(HITT or HIT type 2)


I have had a previous clot – DVT (deep vein thrombosis) and/or PE (pulmonary embolus), is it safe for me to have the vaccine?

There is no evidence that patients with previous history of clots are more at risk of developing this rare effect after the vaccine.  The risk of clots from Covid-19 disease itself is far greater that the risk of this rare adverse effect from vaccination.


I am on the contraceptive pill, and I hear that causes increased risk of clots, can I have the vaccine?

The contraceptive pill is not known to increase the chance of this rare adverse effect with the covid-19 vaccination.


Why have other countries stopped vaccinating with AstraZeneca, is it safe to have?

Every country has its own medicines authority so makes its own decision, based on the information they have.  The UK has the MHRA (Medicines and Healthcare product Regulatory Authority) and JCVI, (Joint Committee on Vaccination and Immunisation). They continue to thoroughly assess all the data and weigh up the risk/benefit of the vaccination.

The decision in the UK is that the benefits of prompt vaccination with the Astra Zeneca Covid-19 vaccine far outweigh the extremely rare risk of adverse effects for individuals aged over 40 years old and those with underlying health conditions putting them at increased risk of Covid-19 disease.  The WHO (World Health Organisation) and the European Medicines Agency have also concluded that the balance of risk/benefit balance is very much in favour of vaccination.


Can I choose to have another vaccine that is not AstraZeneca for my second one?

All those who have received the 1st dose of AstraZeneca should continue to be offered the 2nd dose of Astra Zeneca, irrespective of age, unless major clots were experienced with low platelets after the 1st dose.


Why have under 40 year olds been offered another vaccine?

The risk of severe illness/death from COVID-19 in these younger age groups is very low. Therefore, as a precaution, under 40-year olds without underlying health conditions can be offered another vaccine (if available) for their first Covid-19 vaccine but can still make an informed decision to receive the Astra Zeneca vaccine to receive earlier protection.

People aged 18-39 can proceed with having Astra Zeneca for their second vaccine if they experienced no serious adverse effects after their first vaccination with Astra Zeneca.