mRNA vaccines against SARS-CoV-2 are remarkably effective. Limited information exists about the incidence of adverse events following immunization (AEFI) with their use. We conducted a prospective observational study including data from 704,003 first-doses recipients; 6536 AEFI were reported, of whom 65.1% had at least one neurologic AEFI ( non-serious 99.6%). Thirty-three serious events were reported; 17 (51.5%) were neurologic (observed frequency, 2.4/100,000 doses). At the time of writing this report, 16/17 cases had been discharged without deaths. Our data suggest that the BNT162b2 mRNA COVID-19 vaccine is safe; its individual and societal benefits outweigh the low percentage of serious neurologic AEFI. This information should help to dissipate hesitancy towards this new vaccine platform.

Background and objectives:Information on stroke among SARS-CoV-2 vaccines remains scarce. We report stroke incidence as an adverse event following immunization (AEFI) among recipients of 79,399,446 doses of 6 different SARS-CoV-2 vaccines (BNT162b2, ChAdOx1 nCov-19, Gam-COVID-Vac, CoronaVac, Ad5-nCoV, and Ad26.COV2-S) between December 24, 2020, and August 31, 2021, in Mexico.Methods:Retrospective descriptive study analyzing stroke incidence per million doses among hospitalized adult patients (≥18 years) during an 8-month interval. According to the World Health Organization, AEFIs were defined as clinical events occurring within 30 days following immunization and categorized as either non-serious or serious depending on severity, treatment, and hospital admission requirements. Acute ischemic stroke (AIS), intracerebral hemorrhage (ICH), subarachnoid hemorrhage (SAH), and cerebral venous thrombosis (CVT) cases were collected through a passive epidemiological surveillance system in which local health providers report potential AEFI to the Mexican General Board of Epidemiology. Data were captured using standardized case report formats by an ad-hoc committee appointed by the Mexican Ministry of Health to evaluate potential neurologic AEFI against SARS-COV-2.Results:We included 56 patients (female, 31 [55.5%]) for an overall incidence of 0.71 cases per 1,000,000 administered doses (95% confidence interval [CI] 0.54–0.92); median age was 65 years (interquartile range 55–76); median time from vaccination-to-stroke (of any subtype) was 2 days (interquartile range 1–5); in 27 (48.2%) patients, the event was diagnosed within the first 24 hours following immunization. The most frequent subtype was AIS in 43 patients (75%; 0.54/1,000,000 doses, 95% CI 0.40–0.73) followed by ICH in 9 (16.1%; 0.11/1,000,000 doses, 95% CI 0.06–0.22), and SAH and CVT, each with 2 cases (3.6%; 0.03/1,000,000 doses, 95% CI 0.01–0.09). Overall, the most common risk factors were hypertension in 33 (58.9%) patients and diabetes mellitus in 22 (39.3%); median hospital length of stay was 6 days (IQR 4–13); at discharge, functional outcome was good (modified Rankin Scale of 0–2) in 41.1% of patients; in-hospital mortality rate was 21.4%.Discussion:Stroke is an exceedingly rare AEFI against SARS-CoV-2. Pre-existing stroke risk factors were identified in most patients. Further research is needed to evaluate causal associations between SARS-COV-2 vaccines and stroke.