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Yellow Cards - putting risks into perspective

Updated: Dec 8, 2021

For the last two months, the MHRA has been producing a weekly summary of Yellow Cards linked to COVID-19 vaccines - the early warning system in the UK whereby adverse reactions that may be linked to drugs, vaccines or devices are recorded and centrally collated.

As of 21 March, there had been 40,833 Yellow Cards for the Pfizer/BioNTech vaccine and 99,817 Yellow Cards for the Oxford/Astrazeneca vaccine. Given the number of doses of each, this means the likelihood of a Yellow Card is 3.8 or 6.8 per 1,000 first dose vaccinations.

Table 3.1 lists some of the more likely reactions recorded on Yellow Cards, with the top 20 accounting for 50-65% of all reactions. Some of these are much more likely (5x-7x) with the Oxford/Astrazeneca vaccine, such as tremor and hyperhidrosis, but only account for 1-2% of reactons. The overwhelming majority will not require hospitalisation. The rate of deaths linked on Yellow Cards was 0.02 or 0.03 per 1,000 first vaccinations respectively.

Table 3.1 - frequency of symptoms on Yellow Cards submitted to MHRA by vaccine

To put this into context, as of 1 April in England, there were 111,577 deaths up to 28 days after a COVID-19 test and 393,494 admissions to hospital. Public Health England records that there were 3,807,387 confirmed cases but limited testing, incomplete presentation and asymptomatic infections are likely to mean that many infections were missed. The most recent Nowcasting and Forecasting report at MRC BIostatistics Unit at University of Cambridge estimates that the true number of COVID-19 infections in England on 1 April was 14.6 million. This would imply an infection case fatality rate of 7.6 per 1,000 or a hospitalisation rate of 27 per 1,000.

These figures illustrate clearly how the observed mortality risk of COVID-19 infection is at least 300x the potential linked mortality risk of COVID-19 vaccinations from the Yellow Card reports. More detailed analysis for different age groups will follow in due course. ​

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