FOI release

Freedom of Information request on breakdown of the specific age and sex of those who have experienced suspected blood clots since receiving COVID-19 Vaccine AstraZeneca as well as serious side effects (FOI 21/378 and 21/421)

Published 28 June 2021

7th May 2021 FOI 21/378 and 21/421 Dear Thank you for your two emails dated:

1. 08 April 2021, where you requested an age breakdown and time from vaccination for patients who had blood clots following receipt of the Oxford/AstraZeneca COVID-19 vaccination (FOI 21/378).
2. 13 April 2021, where you requested (I) the date serious side effects like blood clotting were first reported, (II) the date the first 5 clotting cases were reported, and (III) the date that the MHRA published clotting as a potential side-effect following receipt of the Oxford/AstraZeneca COVID19 vaccination (FOI 21/421).

Further to your request, MHRA publishes a weekly summary of Yellow Card reporting which can be found on this link: https://www.gov.uk/government/publications/coronavirus-covid-19-vaccineadverse-reactions/coronavirus-vaccine-summary-of-yellow-card-reporting. In this publication, you will find a breakdown of the age and sex of UK reports of an extremely rare and unlikely to occur specific type of blood clot in the brain, known as cerebral venous sinus thrombosis (CVST) occurring together with low levels of platelets (thrombocytopenia) following vaccination with the COVID-19 Vaccine AstraZeneca.

The estimated number of first doses of COVID-19 Vaccine AstraZeneca administered in the UK by 28 April was 22.6 million and 5.9 million estimated second doses, giving an overall case incidence of 10.5 per million doses. Taking into account the different numbers of patients vaccinated with COVID-19 Vaccine AstraZeneca in different age groups, there is a higher reported incidence rate in the younger adult age groups compared to the older groups. 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. 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.

Although this condition remains extremely rare there appears to be a higher risk in people shortly after the first dose of the AstraZeneca (AZ) vaccine. This is seen slightly more often in younger people and tends to occur between 4 days and 2 weeks following vaccination.

For the majority of reports received the time from receiving a vaccination to when the events occurred were within 4 days to 2 weeks; however, some reports do include an event onset later than 2 weeks whilst others have not been provided. It is important to note that when submitting a Yellow Card, reporters may report the time to onset as the time when the first symptoms began, the time at which an admission occurred or a diagnosis. The MHRA consider all ADR reports in our ongoing analysis regardless of time to onset and look at a range of risk windows in our statistical analysis; we never exclude a case.

It is important to note that Yellow Card reports are not proof of a side effect occurring due to a vaccine but a suspicion by the reporter that the medicine or vaccine may have caused the side effect. Some events may have happened anyway, regardless of vaccination. This is particularly the case when millions of people are vaccinated.

Further to your email on the 13 April, we received the first Yellow Card report of cerebral venous sinus thrombosis (CVST) with concurrent thrombocytopenia in the week commencing 08 February 2021, and it appeared in the weekly summary of Yellow Card reporting on 26 February 2021, which included information on reports received up to the 14 February 2021. This case was considered to be exceptionally rare at that time given that 6.9 million people had received their first dose of COVID-19 AstraZeneca vaccine by 14 February 2021; however, we have continued to review and investigate cases as further evidence has emerged. Since the receipt of the first report we have received further reports of this particular event and these have all been included in the weekly ADR summary. Reports to the Yellow Card scheme can be made at any time regardless of when a suspected side effect may occur, and as a result we can receive retrospective reports.

The MHRA made announcements on 18 March 2021 and 07 April 2021 and as said above included all information in the weekly 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