key: cord-0757351-oi8epg9m
authors: Birhane, Meseret; Bressler, Sara; Chang, Gregory; Clark, Thomas; Dorough, Layne; Fischer, Marc; Watkins, Louise Francois; Goldstein, Jason M.; Kugeler, Kiersten; Langley, Gayle; Lecy, Kristin; Martin, Stacey; Medalla, Felicita; Mitruka, Kiren; Nolen, Leisha; Sadigh, Katrin; Spratling, Robin; Thompson, Gail; Trujillo, Alma
title: COVID-19 Vaccine Breakthrough Infections Reported to CDC — United States, January 1–April 30, 2021
date: 2021-05-28
journal: MMWR Morb Mortal Wkly Rep
DOI: 10.15585/mmwr.mm7021e3
sha: 1ddfe25251568496f9c6a12d68eada30bf6e04fc
doc_id: 757351
cord_uid: oi8epg9m

COVID-19 vaccines are a critical tool for controlling the ongoing global pandemic. The Food and Drug Administration (FDA) has issued Emergency Use Authorizations for three COVID-19 vaccines for use in the United States.* In large, randomized-controlled trials, each vaccine was found to be safe and efficacious in preventing symptomatic, laboratory-confirmed COVID-19 (1-3). Despite the high level of vaccine efficacy, a small percentage of fully vaccinated persons (i.e. received all recommended doses of an FDA-authorized COVID-19 vaccine) will develop symptomatic or asymptomatic infections with SARS-CoV-2, the virus that causes COVID-19 (2-8).

* https://www.fda.gov/emergency-preparedness-and-response/coronavirusdisease-2019-covid-19/covid-19-vaccines † https://www.cdc.gov/vaccines/covid-19/health-departments/breakthroughcases.html concern, § including B.1.1.7 (199; 56%), B.1.429 (88; 25%), B.1.427 (28; 8%), P.1 (28; 8%), and B.1.351 (13; 4%).

As of April 30, 2021, approximately 101 million persons in the United States had been fully vaccinated against COVID-19. ¶ However, during the surveillance period, SARS-CoV-2 transmission continued at high levels in many parts of the country, with approximately 355,000 COVID-19 cases reported nationally during the week of April 24-30, 2021.** Even though FDA-authorized vaccines are highly effective, breakthrough cases are expected, especially before population immunity reaches sufficient levels to further decrease transmission. However, vaccine breakthrough infections occur in only a small fraction of all vaccinated persons and account for a small percentage of all COVID-19 cases (5) (6) (7) (8) . The number of COVID-19 cases, hospitalizations, and deaths that will be prevented among vaccinated persons will far exceed the number of vaccine breakthrough cases. To date, the age and sex distribution of reported vaccine breakthrough infections reflects the fully vaccinated U.S. population. † † The proportion of reported vaccine breakthrough infections attributed to variants of concern has also been similar to the proportion of these variants circulating throughout the United States. During March 28-April 10, 2021, the aforementioned variants of concern accounted for 70% of the weighted estimates of SARS-CoV-2 lineages submitted to CDC's national genomic surveillance. § § The findings in this report are subject to at least two limitations. First, the number of reported COVID-19 vaccine breakthrough cases is likely a substantial undercount of all SARS-CoV-2 infections among fully vaccinated persons. The national surveillance system relies on passive and voluntary reporting, and data might not be complete or representative. Many persons with vaccine breakthrough infections, especially those who are asymptomatic or who experience mild illness, might not seek testing. Second, SARS-CoV-2 sequence data are available for only a small proportion of the reported cases.

Beginning (1) (2) (3) (4) (5) (6) (7) (8) . CDC recommends that all persons aged ≥12 years be vaccinated with an FDA-authorized COVID-19 vaccine ¶ ¶ (10) .

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