Assessing Case Fatality on Cases of Thrombosis with Thrombocytopenia Following COVID-19 Vaccine AstraZeneca (Vaxzevria) in the United Kingdom: A Review of Spontaneously Reported Data

11 August 2022

Samantha Lane & Saad Shakir

As we have said before, pharmacovigilance has moved on from the initial phase of assessing the benefits/risks (B/R) of vaccines and treatments for COVID-19 with the available (limited) data at the time. Pharmacovigilance now has different, more long-term objectives. We are now trying to further our understanding of the nature, risk factors, preventability, frequency, and other characteristics of serious adverse drug reactions (ADRs).

More studies and reviews will facilitate better understanding of the ADRs and the B/R balance of the COVID-19 vaccines and treatment. This will allow better public health decisions, patients selection, clinical management, and outcomes. Good research will stimulate better research.

The DSRU has recently published research titled “Assessing Case Fatality on Cases of Thrombosis with Concurrent Thrombocytopenia Following COVID-19 Vaccine AstraZeneca (Vaxzevria) in the United Kingdom: A Review of Spontaneously Reported Data.”

Thrombotic thrombocytopenia syndrome (TTS) events have been reported very rarely following adenoviral vector vaccines, including the COVID-19 Vaccine AstraZeneca (Vaxzevria). Clinical and demographic characteristics of the affected people, including the outcomes of TTS events, need to be examined using available information to better understand aspects of this association.

The objective of this study was therefore to analyse clinical and demographic information of TTS events, including calculating the case fatality of reported cases of TTS by age and sex, using spontaneously reported data from the UK’s Yellow Card spontaneous reporting system of suspected adverse drug reactions.

TTS events reported to the Yellow Card scheme were extracted at weekly time points between 12 May 2021 and 25 May 2022. Cumulative numbers of TTS cases and deaths were recorded for each weekly interval, overall and stratified by age, sex, and vaccine dose.

Up to 25 May 2022, 443 cases of TTS (81 fatal, 18.28%) had been reported to the UK Yellow Card scheme. Events more frequently occurred following the first vaccine dose. No trends were observed for case fatality overall, or by age or sex.

In the UK, case fatality of TTS events reported to the Medicines and Health products Regulatory Agency (MHRA) following Vaxzevria has been approximately 17–18% since May 2021. There were no statistical differences in fatality based on age or sex. Most reports followed the first vaccine dose; none have been reported following a third dose to date, although Vaxzervia was not recommended for a third dose of COVID-19 vaccine in the UK. TTS remains very rare, and benefits of vaccination outweigh the risks.

The world was lucky that COVID-19 vaccines and treatments were mostly effective with few very rare short-term ADRs. The main advantages of both vaccines and treatments were that they reduced serious morbidity and mortality for COVID-19 significantly, with an acceptable B/R balance.

The full text of this published research is available via Drug Safety.


The contents of this article have not been peer-reviewed; it should not replace individual clinical judgement, and the sources cited should be checked. The views expressed in this commentary represent the views of the authors. These views are not a substitute for professional medical advice.