Alliance for Pandemic Preparedness

May 25, 2021

COVID-19 Vaccine Breakthrough Infections Reported to CDC — United States, January 1–April 30, 2021

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  • A total of 10,262 SARS-CoV-2 vaccine breakthrough cases were reported to the CDC across the US as of April 30, 2021, out of approximately 101 million fully vaccinated individuals (0.01%). 27% of vaccine breakthrough infections were asymptomatic. Of the 10% of infected individuals who were hospitalized, of whom 29% were asymptomatic or hospitalized for reasons unrelated to COVID-19. 2% of infections resulted in death (median age 82 years), of whom 18% were asymptomatic or died due to reasons unrelated to COVID-19. Of the 555 breakthrough cases with sequence data, 356 (64%) were identified as variants of concern, including B.1.1.7 (56%), B.1.429 (25%), B.1.427 (8%), P.1 (8%), and B.1.351 (4%). High levels of SARS-CoV-2 transmission were observed during the surveillance period, with approximately 355,000 COVID-19 cases reported nationally during the week of April 24–30, 2021.

Birhane et al. (May 25, 2021). COVID-19 Vaccine Breakthrough Infections Reported to CDC — United States, January 1–April 30, 2021. MMWR. https://doi.org/10.15585/mmwr.mm7021e3