• Mark G Thompson, Edward Stenehjem, Shaun Grannis, Sarah W Ball, Allison L Naleway, Toan C Ong, Malini B DeSilva, Karthik Natarajan, Catherine H Bozio, Ned Lewis, Kristin Dascomb, Brian E Dixon, Rebecca J Birch, Stephanie A Irving, Suchitra Rao, Elyse Kharbanda, Jungmi Han, Sue Reynolds, Kristin Goddard, Nancy Grisel, William F Fadel, Matthew E Levy, Jill Ferdinands, Bruce Fireman, Julie Arndorfer, Nimish R Valvi, Elizabeth A Rowley, Palak Patel, Ousseny Zerbo, Eric P Griggs, Rachael M Porter, Maria Demarco, Lenee Blanton, Andrea Steffens, Yan Zhuang, Natalie Olson, Michelle Barron, Patricia Shifflett, Stephanie J Schrag, Jennifer R Verani, Alicia Fry, Manjusha Gaglani, Eduardo Azziz-Baumgartner, and Nicola P Klein.
• From the Centers for Disease Control and Prevention COVID-19 Response Team, Atlanta (M.G.T., C.H.B., S. Reynolds, J.F., P.P., E.P.G., R.M.P., L.B., A.S., N.O., S.J.S., J.R.V., A.F., E.A.-B.); the Division of Infectious Diseases and Clinical Epidemiology, Intermountain Healthcare, Salt Lake City (E.S., K.D., N.G., J.A.); the Center for Biomedical Informatics, Regenstrief Institute (S.G., B.E.D., W.F.F., N.R.V.), Indiana University School of Medicine (S.G.), and Indiana University Richard M. Fairbanks School of Public Health (B.E.D., W.F.F., N.R.V.) - all in Indianapolis; Westat, Rockville, MD (S.W.B., R.J.B., M.E.L., E.A.R., M.D., Y.Z., P.S.); the Kaiser Permanente Northwest Center for Health Research, Portland, OR (A.L.N., S.A.I.); the Department of Medicine, Anschutz Medical Campus, University of Colorado, Aurora (T.C.O., S. Rao, M.B.); HealthPartners Institute, Minneapolis (M.B.D., E.K.); the Department of Biomedical Informatics, Columbia University Irving Medical Center (K.N., J.H.), and New York-Presbyterian Hospital (K.N.) - both in New York; the Vaccine Study Center, Division of Research, Kaiser Permanente Northern California, Oakland (N.L., K.G., B.F., O.Z., N.P.K.); and Baylor Scott and White Health, Texas A&M University College of Medicine, Temple, TX (M.G.).
• N. Engl. J. Med. 2021 Oct 7; 385 (15): 135513711355-1371.

BackgroundThere are limited data on the effectiveness of the vaccines against symptomatic coronavirus disease 2019 (Covid-19) currently authorized in the United States with respect to hospitalization, admission to an intensive care unit (ICU), or ambulatory care in an emergency department or urgent care clinic.MethodsWe conducted a study involving adults (≥50 years of age) with Covid-19-like illness who underwent molecular testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We assessed 41,552 admissions to 187 hospitals and 21,522 visits to 221 emergency departments or urgent care clinics during the period from January 1 through June 22, 2021, in multiple states. The patients' vaccination status was documented in electronic health records and immunization registries. We used a test-negative design to estimate vaccine effectiveness by comparing the odds of a positive test for SARS-CoV-2 infection among vaccinated patients with those among unvaccinated patients. Vaccine effectiveness was adjusted with weights based on propensity-for-vaccination scores and according to age, geographic region, calendar time (days from January 1, 2021, to the index date for each medical visit), and local virus circulation.ResultsThe effectiveness of full messenger RNA (mRNA) vaccination (≥14 days after the second dose) was 89% (95% confidence interval [CI], 87 to 91) against laboratory-confirmed SARS-CoV-2 infection leading to hospitalization, 90% (95% CI, 86 to 93) against infection leading to an ICU admission, and 91% (95% CI, 89 to 93) against infection leading to an emergency department or urgent care clinic visit. The effectiveness of full vaccination with respect to a Covid-19-associated hospitalization or emergency department or urgent care clinic visit was similar with the BNT162b2 and mRNA-1273 vaccines and ranged from 81% to 95% among adults 85 years of age or older, persons with chronic medical conditions, and Black or Hispanic adults. The effectiveness of the Ad26.COV2.S vaccine was 68% (95% CI, 50 to 79) against laboratory-confirmed SARS-CoV-2 infection leading to hospitalization and 73% (95% CI, 59 to 82) against infection leading to an emergency department or urgent care clinic visit.ConclusionsCovid-19 vaccines in the United States were highly effective against SARS-CoV-2 infection requiring hospitalization, ICU admission, or an emergency department or urgent care clinic visit. This vaccine effectiveness extended to populations that are disproportionately affected by SARS-CoV-2 infection. (Funded by the Centers for Disease Control and Prevention.).Copyright © 2021 Massachusetts Medical Society.

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