Post-authorisation study on AstraZeneca Covid vaccine completed!

The COVID-19 vaccines were developed and tested rapidly, meaning that it was especially important to monitor their safety and effectiveness in the post-authorisation setting. The DSRU conducted a major post-authorisation safety study (PASS) on the AstraZeneca Covid vaccine, for which the first participants were recruited in March 2021 and the final report was submitted to the MHRA in January 2024. Results of the study will be published soon, but in the meantime we asked the Study Manager, Dr Alison Evans, to tell us about the study:

Q. What was the aim of this study?

A: To monitor the safety and utilisation of the COVID-19 Vaccine AstraZeneca (AZD1222) administered to vaccinees under real-world use in the UK.

Q: What was the study design?

A: The study was a non-interventional post-authorisation active surveillance study

Q: Could you outline the study method?

A: Vaccinees were recruited via vaccination sites, social media and advertisements within the UK, supported by the National Institute for Health Research Clinical Research Networks. Participants were eligible to sign up to the study if they had received AZD1222 as their first COVID-19 vaccine dose within 6 weeks and provided consent. At the datalock point for the final report (6th April 2023), a total of 17945 participants were eligible and provided consent. Participants were contacted to report any symptoms or conditions experienced following vaccination at weeks 1, 4 and 14 and then months 6, 9, 12 and 18 after the first AZD1222 dose vaccination, via electronic data capture forms.

Q: What are the findings of the study?

A: The most frequently reported adverse event of special interest was loss of smell or taste, which was observed more than expected when compared to pre-COVID-19 pandemic background rates in the UK. However, it is likely that this was a reflection of participants experiencing symptoms of COVID-19 infection. There were also more cases of anaphylaxis reported in this study than were expected. This possible side effect is listed in the Patient Information Leaflet for AZD1222.  

Q: What are the strengths of this study?

A: The safety and effectiveness of new medicines and vaccines is tested in clinical trials before the products are approved for use in the UK. However it is essential to continue to monitor medicines and vaccines using observational studies, such as this one, after authorisation in order to find out how they perform in real-world conditions. This large-scale active surveillance study allowed for real time safety evaluation and signal detection during the pandemic as adverse event data was shared in real-time with the UK medicines regulator, the MHRA. 

This was a large study that was set up in record time, but it was possible to adapt the study design to respond and reflect changes in the UK vaccination roll out, including the introduction of the third COVID-19 vaccine dose and subsequent COVID-19 vaccinations.

With consent from the participant, we were able to seek further information from the vaccinees General Practitioner for adverse events assessed as serious and/or considered to be an adverse event of special interest.