Multi-national European cohort event monitoring studies on COVID-19 vaccines


Published results from the multi-national European cohort event monitoring show that most participants experience an adverse reaction after the first dose of the COVID-19 vaccines. The vast majority of these reactions are common, well-known reactions which improved within a few days. Participants with a prior SARS-CoV-2 infection were more likely to report an adverse event after their first dose of a COVID-19 vaccine.

Frequency, timing and predictors of adverse reactions
Nine European countries were included in the analysis on frequency and timing of adverse reactions after the first, second and booster vaccination of the COVID-19 vaccines. Solicited adverse reactions were reported by almost three quarters (74.32%, 95%CI 73.82—74.81) of participants. The frequency of reporting at least one adverse reaction was higher after the first dose, except for one vaccine brand where participants reported more adverse reactions after the second dose. The male sex and increasing age had a lower contribution to adverse reactions. The median time to onset for adverse reactions was 14 hours for the first dose, this was slightly longer for the second dose and for the booster. Time to recovery was generally within a few days, however several adverse reactions such as fatigue were reported with a long time to recovery.

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Adverse reactions in persons with a prior SARS-CoV-2 infection
Data was included from eleven European countries. This study showed low frequency of serious adverse reactions in persons with a prior SARS-CoV-2 infection, nevertheless these persons were more likely to report experiencing an adverse reaction than persons without a prior infection for the first dose (3470 [89.6%] vs. 2916 [75.3%]) and booster (614 [68.2%] vs. 546 [60.6%]) COVID-19 vaccine. Younger subjects and women were more likely to report an adverse reaction after COVID-19 vaccination.

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