Vaccine effectiveness (VE) estimates are needed to monitor the effect of updated COVID-19 vaccinations, say Wiegand, et al. (2026) who sought to assess the effectiveness of 2024-2025 COVID-19 vaccines against medically attended COVID-19 among adults 18 years and older in the U.S. This case-control study with a test-negative design included patient encounters with a COVID-19–like illness discharge diagnosis code and a molecular or antigen SARS-CoV-2 test within 10 days before to 3 days after the encounter date, from Sept. 5, 2024, to Sept. 2, 2025. Encounters were captured in VISION (Virtual SARS-CoV-2, Influenza, and Other Respiratory Viruses Network), a multisite, electronic medical record–based network of health care systems, including 381 emergency department/urgent care (ED/UC) departments and 246 hospitals in six states.

In 333,262 eligible ED/UC encounters (median [IQR] age of patients, 54 [35-72] years; 60% female) and 97,663 eligible hospitalizations among immunocompetent adults 18 years and older (median [IQR] age of patients, 72 [59-81] years; 53% female), estimated VE was 26% (95% CI, 23%-29%) against COVID-19–associated ED/UC encounters, 35% (95% CI, 30%-40%) against COVID-19–associated hospitalization, and 41% (95% CI, 28%-51%) against COVID-19–associated critical illness 7 to 299 days after vaccination. Among immunocompetent adults 65 years and older (122 663 ED/UC encounters and 63 958 hospitalizations), estimated VE was 26% (95% CI, 22%-30%) against COVID-19–associated ED/UC encounters, 35% (95% CI, 29%-40%) against COVID-19–associated hospitalization, and 41% (95% CI, 28%-52%) against COVID-19–associated critical illness 7 to 299 days after vaccination. Among 32,629 hospitalizations in immunocompromised adults 18 years and older, estimated VE against COVID-19–associated hospitalization was 24% (95% CI, 13%-34%). VE estimates waned with more time since vaccination.

In this test-negative case-control study, 2024-2025 COVID-19 vaccination was associated with reduced likelihood of medically attended COVID-19–associated outcomes among immunocompetent and immunocompromised adults, highlighting the importance of adults receiving recommended COVID-19 vaccinations.

Reference: Wiegand RE, et al. Estimated Effectiveness of 2024-2025 COVID-19 Vaccines in Adults JAMA Intern Med. Published Online: June 15, 2026
doi: 10.1001/jamainternmed.2026.1936