{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,22]],"date-time":"2026-10-22T15:18:00Z","timestamp":1792682280001,"version":"4.5.0"},"reference-count":14,"publisher":"American Medical Association (AMA)","issue":"5","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["JAMA Netw Open"],"abstract":"\n Importance<\/jats:title>\n COVID-19 vaccine effectiveness (VE) is typically studied in the context of reducing the risk of severe illness and death. Few studies have estimated VE in preventing transmission and infection with current levels of SARS-CoV-2 population immunity.<\/jats:p>\n <\/jats:sec>\n \n Objective<\/jats:title>\n To estimate COVID-19 VE against transmission and infection within households.<\/jats:p>\n <\/jats:sec>\n \n Design, Setting, and Participants<\/jats:title>\n This cohort study was a prospective, case-ascertained household transmission study (performed in New York, Tennessee, and Washington) in which the first household member with confirmed SARS-CoV-2 infection (primary case participant) was identified through outpatient settings and enrolled with their household contacts from January 1, 2024, to January 31, 2025. Participants provided demographic information, and COVID-19 vaccination history was verified by study staff. After enrollment, participants were instructed to collect daily nasal swabs for 10 days regardless of symptoms. Nasal swabs were tested for SARS-CoV-2 via reverse transcription\u2013polymerase chain reaction.<\/jats:p>\n <\/jats:sec>\n \n Exposure<\/jats:title>\n COVID-19 vaccination history in primary case participants and household contacts categorized as time from most recent vaccination to COVID-19 onset in the primary case participant (\u22646 months, 7-12 months, &amp;gt;12 months, and unvaccinated [reference group]).<\/jats:p>\n <\/jats:sec>\n \n Main Outcomes and Measures<\/jats:title>\n Household contacts were considered infected if at least 1 swab tested positive for SARS-CoV-2. Secondary infection risk was calculated as the number of infected contacts divided by the total number of contacts. Adjusted relative risk (ARR) of infection was estimated using a multivariable Poisson regression model, with generalized estimating equations accounting for household-level clustering. Vaccine effectiveness was calculated as 1 minus the ARR of the primary case participant and household contacts\u2019 vaccination status to estimate VE against transmission and against infection, respectively.<\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n This analysis included 362 primary case participants (median [IQR] age,\u200935 [10-53] years; 199 female [55.0%]) and 763 household contacts (median [IQR] age,\u200929 [12-44] years; 399 female [52.3%]). SARS-CoV-2 infection was detected in 476 household contacts during follow-up for a secondary infection risk of 62.4% (95% CI,\u200958.7%-65.5%). Household contacts of primary case participants vaccinated 6 months or less before onset had a lower infection risk compared with contacts of unvaccinated primary case participants (ARR,\u20090.57 [95% CI, 0.35-0.93]). There was no statistically significant difference in infection risk based on vaccination status of household contacts.<\/jats:p>\n <\/jats:sec>\n \n Conclusions and Relevance<\/jats:title>\n In this cohort study, recent COVID-19 vaccination was associated with a reduced risk of SARS-CoV-2 transmission. These findings suggest that COVID-19 vaccination may have an indirect benefit of decreasing transmission and thus reducing overall exposure to SARS-CoV-2.<\/jats:p>\n <\/jats:sec>","DOI":"10.1001\/jamanetworkopen.2026.12609","type":"journal-article","created":{"date-parts":[[2026,5,15]],"date-time":"2026-05-15T15:30:28Z","timestamp":1778859028000},"page":"e2612609","source":"Crossref","is-referenced-by-count":4,"title":["Recent COVID-19 Vaccination and Risk of SARS-CoV-2 Transmission"],"prefix":"10.1001","volume":"9","author":[{"given":"Sara C.","family":"Benist","sequence":"first","affiliation":[{"name":"National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia"},{"name":"Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sarah E.","family":"Smith-Jeffcoat","sequence":"additional","affiliation":[{"name":"National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"H. Keipp","family":"Talbot","sequence":"additional","affiliation":[{"name":"Vanderbilt University Medical Center, Nashville, Tennessee"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yuwei","family":"Zhu","sequence":"additional","affiliation":[{"name":"Vanderbilt University Medical Center, Nashville, Tennessee"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jonathan E.","family":"Schmitz","sequence":"additional","affiliation":[{"name":"Vanderbilt University Medical Center, Nashville, Tennessee"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Theresa A.","family":"Scott","sequence":"additional","affiliation":[{"name":"Vanderbilt University Medical Center, Nashville, Tennessee"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Melissa S.","family":"Stockwell","sequence":"additional","affiliation":[{"name":"Columbia University Irving Medical Center, New York, New York"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Son H.","family":"McLaren","sequence":"additional","affiliation":[{"name":"Columbia University Irving Medical Center, New York, New York"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ellen D.","family":"Sano","sequence":"additional","affiliation":[{"name":"Columbia University Irving Medical Center, New York, New York"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Celibell Y.","family":"Vargas","sequence":"additional","affiliation":[{"name":"Columbia University Irving Medical Center, New York, New York"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ana","family":"Valdez de Romero","sequence":"additional","affiliation":[{"name":"Columbia University Irving Medical Center, New York, New York"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Helen Y.","family":"Chu","sequence":"additional","affiliation":[{"name":"University of Washington, Seattle, Washington"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Janet A.","family":"Englund","sequence":"additional","affiliation":[{"name":"University of Washington, Seattle, Washington"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Erica","family":"Clark","sequence":"additional","affiliation":[{"name":"University of Washington, Seattle, Washington"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Melissa P.","family":"MacMillan","sequence":"additional","affiliation":[{"name":"University of Washington, Seattle, Washington"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Adam S.","family":"Lauring","sequence":"additional","affiliation":[{"name":"Department of Internal Medicine, University of Michigan, Ann Arbor"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"E. Ivy","family":"Oyegun","sequence":"additional","affiliation":[{"name":"National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"J. Bradford","family":"Bertumen","sequence":"additional","affiliation":[{"name":"National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Carlos G.","family":"Grijalva","sequence":"additional","affiliation":[{"name":"Vanderbilt University Medical Center, Nashville, Tennessee"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hannah L.","family":"Kirking","sequence":"additional","affiliation":[{"name":"National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"10","published-online":{"date-parts":[[2026,5,15]]},"reference":[{"issue":"15","key":"zoi260381r2","doi-asserted-by":"publisher","first-page":"1355","DOI":"10.1056\/NEJMoa2110362","article-title":"Effectiveness of COVID-19 vaccines in ambulatory and inpatient care settings.","volume":"385","author":"Thompson","year":"2021","journal-title":"N Engl J Med"},{"issue":"6","key":"zoi260381r3","doi-asserted-by":"publisher","first-page":"73","DOI":"10.15585\/mmwr.mm7406a1","article-title":"Interim estimates of 2024-2025 COVID-19 vaccine effectiveness among adults aged =18 years - VISION and IVY Networks, September 2024-January 2025.","volume":"74","author":"Link-Gelles","year":"2025","journal-title":"MMWR Morb Mortal Wkly Rep"},{"issue":"6","key":"zoi260381r4","doi-asserted-by":"publisher","first-page":"1603","DOI":"10.1093\/aje\/kwae334","article-title":"Reduced risk of SARS-CoV-2 infection among household contacts with recent vaccination and past COVID-19 infection: results from two multi-site case-ascertained household transmission studies.","volume":"194","author":"Rolfes","year":"2025","journal-title":"Am J Epidemiol"},{"issue":"10","key":"zoi260381r5","doi-asserted-by":"publisher","first-page":"789","DOI":"10.1093\/oxfordjournals.aje.a009196","article-title":"Study designs for evaluating different efficacy and effectiveness aspects of vaccines.","volume":"146","author":"Halloran","year":"1997","journal-title":"Am J Epidemiol"},{"issue":"4","key":"zoi260381r6","doi-asserted-by":"publisher","first-page":"340","DOI":"10.1056\/NEJMoa2115481","article-title":"Duration of protection against mild and severe disease by COVID-19 vaccines.","volume":"386","author":"Andrews","year":"2022","journal-title":"N Engl J Med"},{"issue":"3","key":"zoi260381r7","doi-asserted-by":"publisher","first-page":"240","DOI":"10.3390\/vaccines12030240","article-title":"Vaccinated COVID-19 index cases are less likely to transmit SARS-CoV-2 to their household contacts: a cohort study.","volume":"12","author":"Godoy","year":"2024","journal-title":"Vaccines (Basel)"},{"issue":"12","key":"zoi260381r9","doi-asserted-by":"publisher","first-page":"2893","DOI":"10.1016\/j.immuni.2021.09.011","article-title":"mRNA vaccination of naive and COVID-19-recovered individuals elicits potent memory B cells that recognize SARS-CoV-2 variants.","volume":"54","author":"Sokal","year":"2021","journal-title":"Immunity"},{"issue":"4","key":"zoi260381r10","doi-asserted-by":"publisher","first-page":"e743","DOI":"10.1093\/infdis\/jiaf007","article-title":"Effectiveness of mRNA COVID-19 vaccines and hybrid immunity in preventing SARS-CoV-2 infection and symptomatic COVID-19 among adults in the United States.","volume":"231","author":"Feldstein","year":"2025","journal-title":"J Infect Dis"},{"issue":"5","key":"zoi260381r11","doi-asserted-by":"publisher","first-page":"408","DOI":"10.1001\/jama.2023.27022","article-title":"Effectiveness of bivalent mRNA COVID-19 vaccines in preventing SARS-CoV-2 infection in children and adolescents aged 5 to 17 years.","volume":"331","author":"Feldstein","year":"2024","journal-title":"JAMA"},{"key":"zoi260381r12","doi-asserted-by":"publisher","DOI":"10.5888\/pcd18.210123","article-title":"Underlying medical conditions and severe illness among 540,667 adults hospitalized with COVID-19, March 2020-March 2021.","volume":"18","author":"Kompaniyets","year":"2021","journal-title":"Prev Chronic Dis"},{"issue":"2","key":"zoi260381r13","doi-asserted-by":"publisher","DOI":"10.1093\/ofid\/ofaa638","article-title":"Risk of clinical severity by age and race\/ethnicity among adults hospitalized for COVID-19-United States, March-September 2020.","volume":"8","author":"Pennington","year":"2020","journal-title":"Open Forum Infect Dis"},{"issue":"7","key":"zoi260381r14","doi-asserted-by":"publisher","first-page":"911","DOI":"10.1093\/cid\/cir007","article-title":"\u201cHerd immunity\u201d: a rough guide.","volume":"52","author":"Fine","year":"2011","journal-title":"Clin Infect Dis"},{"key":"zoi260381r1","unstructured":"Preliminary 2024-2025 U.S. COVID-19 Burden Estimates. 2024-2025. Centers for Disease Control and Prevention. Updated June 13, 2025. Accessed June 13, 2025. https:\/\/data.cdc.gov\/Public-Health-Surveillance\/Preliminary-2024-2025-U-S-COVID-19-Burden-Estimate\/ahrf-yqdt\/about_data"},{"key":"zoi260381r8","unstructured":"2022\u20132023 Nationwide blood donor seroprevalence survey combined infection- and vaccination-induced seroprevalence estimates. Centers for Disease Control and Prevention. Updated February 23, 2025. 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