Blog: Reporting rate of serious allergic reactions with the Pfizer/BioNTech vaccine – to put things in perspective

Saad Shakir writes:

A reporting rate from spontaneous reporting can be biased because of inaccuracies in the numerator and denominator.  But it is an acceptable estimate for this vaccine because of the intense monitoring of allergic reactions and the accurate available real time numbers of vaccinated people.   In the US six cases of severe allergic skin reactions were reported in 250,000 vaccinees.

Our DSRU colleague Debabrata Roy calculated the proportion:  Proportion with severe allergic reaction = 0.000024 with a 95% CI (0.0000 to 0.0001).

This equates to approximately 1.2 cases per 50,000 vaccinees.  In pharmacovigilance adverse events with a frequency of less than 1/10,000 are considered very rare.

There has been no report of an adverse event with a fatal outcome with this vaccine in clinical trials or real world use vaccination anywhere in the world.