Surveillance of adverse events following administration of COVID-19 mRNA vaccines


On 3 September, JAMA published an interim analysis of safety surveillance data from the Vaccine Safety Datalink. Approximately 10,162,227 vaccine-eligible members of eight participating U.S. health plans were monitored, with administrative data updated weekly and supplemented with medical record review of selected outcomes from 14 December 2020 through 26 June 2021. The objective was to monitor 23 serious events weekly, following administration of the BNT162b2 (Pfizer-BioNTech) or mRNA-1273 (Moderna) vaccine, comparing those vaccinated with a risk interval of 21 days after vaccination with those vaccinated with the comparison interval of between 22 to 42 days.

A comparison was made of the incidence of serious events, including acute myocardial infarction, Bell's palsy, cerebral venous sinus thrombosis, Guillain-Barré syndrome, myocarditis/pericarditis, pulmonary embolism, stroke, and thrombosis with thrombocytopenia syndrome. For four serious events (acute respiratory distress syndrome, anaphylaxis, multisystem inflammatory syndrome in children and adults, and narcolepsy), only descriptive analyses were performed. 

A total of 11,845,128 doses of COVID-19 mRNA vaccines (57% BNT162b2; 6,175,813 first doses and 5,669,315 second doses) were administered to 6.2 million people (mean age, 49 years; 54% women). The incidence of events in the studied population per million person-years during the risk versus comparison intervals for ischemic stroke was 1,612 versus 1,781 (RR, 0.97; 95% CI, 0.87-1.08); for appendicitis, 1,179 versus 1,345 (RR, 0.82; 95% CI, 0.730.93); and for acute myocardial infarction, 935 versus 1,030 (RR, 1.02; 95% CI, 0.89-1.18). No vaccine-outcome association met the pre-specified requirement for a signal. Incidence of confirmed anaphylaxis was 4.8 (95% CI, 3.2-6.9) per million doses of BNT162b2 and 5.1 (95% CI, 3.3-7.6) per million doses of mRNA-1273.

The authors conclude, based on this interim analysis of surveillance of mRNA COVID-19 vaccines, that the incidence of selected serious outcomes was not significantly higher one to 21 days postvaccination compared with 22 to 42 days postvaccination. While CIs were wide for many outcomes, surveillance is ongoing.

Source: Klein NP, Lewis N, Goddard K, et al. Surveillance for Adverse Events After COVID-19 mRNA Vaccination.

JAMA. Published online 3 September 2021. doi: 10.1001/jama.2021.15072. Available at:    

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