FOI release

Freedom of Information request on thromboembolic events with concurrent thrombocytopenia post AstraZeneca COVID-19 vaccine (FOI 21-464)

Published 13 August 2021

10th June 2021 FOI 21/464

Dear

Thank you for your Freedom of Information (FOI) request regarding thromboembolic events with concurrent thrombocytopenia post COVID-19 Vaccine AstraZeneca.

As you will know, we publish a weekly COVID-19 ADR summary alongside analysis prints for each vaccine, these can be found here: https://www.gov.uk/government/publications/coronavirus-covid-19-vaccine-adverse-reactions/coronavirusvaccine-summary-of-yellow-card-reporting. It currently pertains to data received up to and including the 5th May 2021. This contains details regarding specific reports including thrombo-embolic events with concurrent low platelets, including a breakdown by patient age and sex.

In your emails you discuss calculations of incidence based on the information published by MHRA and PHE. It’s important to note that Yellow Card reports can be submitted at any time after a suspected adverse reaction has occurred. We receive many retrospective reports that happened earlier in the campaign and we are following up with reporters on many reports to gain further information, which when received may then indicate thromboembolism with concurrent thrombocytopenia. Additionally, the onset of these events is usually between 4 and 10 days meaning that any new reports received will be from vaccinations in previous weeks. Therefore, the incidence at which these events occur cannot be calculated based on doses received solely in the previous week.

The estimated number of first doses of COVID-19 Vaccine AstraZeneca administered in the UK by 5th May was 23.3 million and the estimated number of second doses was 7.5 million. The overall incidence after first or unknown doses was 10.9 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 compared to the older groups. Published data on the age stratified incidence rate based on the MHRA data, alongside data on the estimated benefits of the vaccine under different assumptions, are presented by the Winton Centre for Risk and Evidence Communication and can be found here: https://wintoncentre.maths.cam.ac.uk/news/latest-data-mhra-blood-clots-associated-astra-zeneca-covid-19-vaccine/.

We advise 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. 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.

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,

Vigilance and Risk Management of Medicine