FOI release

Freedom of Information request on blood clots following the second AstraZeneca vaccine (FOI 21-526)

Published 13 August 2021

11th June 2021 FOI 21/526

Dear

Thank you for your Freedom of Information (FOI) request dated 12th May 2021, where you requested the following information:

“how many blood clots there have been from the second Astra Zeneca vaccine.”

Up to 2 June 2021, the MHRA had received Yellow Card reports of 372 cases of major thromboembolic events (blood clots) with concurrent thrombocytopenia (low platelet counts) in the UK following vaccination with COVID-19 Vaccine AstraZeneca. These events occurred in 200 women and 169 men aged from 18 to 93 years and the overall case fatality rate was 18% with 66 deaths. 23 cases have been reported after a second dose.

Cerebral venous sinus thrombosis was reported in 135 cases (average age 46 years) and 237 had other major thromboembolic events (average age 54 years) with concurrent thrombocytopenia. The estimated number of first doses of COVID-19 Vaccine AstraZeneca administered in the UK by 2 June was 24.5 million and the estimated number of second doses was 15.7 million.

The overall incidence after first or unknown doses was 14.2 per million doses. Taking into account the different numbers of patients vaccinated with COVID-19 Vaccine AstraZeneca in different age groups, the data shows that there is a higher reported incidence rate in the younger adult age groups following the first dose compared to the older groups. (19.8 per million doses in those aged 18-49 years compared to 10.3 per million doses in those aged 50 years and over). The MHRA advises that this evolving evidence should be taken into account when considering the use of the vaccine. There is now some evidence that the reported incidence rate is higher in females compared to men although this is not seen across all age groups and the difference remains small.

The overall incidence after second doses was 1.5 per million doses. Taking into account the different numbers of patients vaccinated with COVID-19 Vaccine AstraZeneca in different age groups, the data shows that there is a lower reported incidence rate in younger adult age groups following the second dose compared to the older groups (0.6 per million doses in those aged 18-49 years compared to 1.5 per million doses in those aged 50 years and over). The number of second doses given to those in the 18-49 years age group is estimated to be 3.3 million while an estimated 12.5 million second doses have been given to patients aged 50+ years. These rates should not be directly compared to the incidence rates reported after the first dose as the time for follow-up and identification of cases after second doses is more limited and differs across age groups. However, the data are reassuring at this stage and suggest that the reported incidence rate following a second dose is smaller than that seen following a first dose. These reports have also been analysed by the Government’s independent advisory body, the COVID-19 Vaccines Benefit Risk Expert Working Group, which includes lay representatives and advice from leading haematologists.

On the basis of this ongoing review, the advice remains that the benefits of the vaccine outweigh the risks in the majority of people.

Please note this information is now included in our published summary of Yellow Card reporting: https://www.gov.uk/government/publications/coronavirus-covid-19-vaccine-adverse-reactions/coronavirus-vaccine-summary-of-yellow-card-reporting

I hope the information provided is helpful, but if you are dissatisfied with the handling of your request, you have the right to ask for an internal review. Internal review requests should be submitted within two months of the date of this response; and can be addressed to this email address.

Yours sincerely,

FOI Team, Vigilance and Risk Management of Medicines Division