Effectiveness of the Ad26.COV2.S (Johnson & Johnson) Coronavirus Disease 2019 (COVID-19) Vaccine for Preventing COVID-19 Hospitalizations and Progression to High Disease Severity in the United States.

Background . Adults in the United States (US) began receiving the adenovirus vector coronavirus disease 2019 (COVID-19) vaccine, Ad26.COV2.S (Johnson & Johnson [Janssen]), in February 2021. We evaluated Ad26.COV2.S vaccine effectiveness (VE) against COVID-19 hospitalization and high disease severity during the first 10 months of its use. Methods . In a multicenter case-control analysis of US adults (≥18 years) hospitalized 11 March to 15 December 2021, we estimated VE against susceptibility to COVID-19 hospitalization (VEs), comparing odds of prior vaccination with a single dose Ad26.COV2.S vaccine between hospitalized cases with COVID-19 and controls without COVID-19. Among hospitalized patients with COVID-19, we estimated VE against disease progression (VEp) to death or invasive mechanical ventilation (IMV), comparing odds of prior vaccination between patients with and without progression. Results . After excluding patients receiving mRNA vaccines, among 3979 COVID-19 case-patients (5% vaccinated with Ad26.COV2.S) and 2229 controls (13% vaccinated with Ad26.COV2.S), VEs of Ad26.COV2.S against COVID-19 hospitalization was 70% (95% confidence interval [CI]: 63-75%) overall, including 55% (29-72%) among immunocompromised patients, and 72% (64-77%) among immunocompetent patients, for whom VEs was similar at 14-90 days (73% [59-82%]), 91-180 days (71% [60-80%]), and 181-274 days (70% [54-81%]) postvaccination. Among hospitalized COVID-19 case-patients, VEp was 46% (18-65%) among immunocompetent patients. Conclusions . The Ad26.COV2.S COVID-19 vaccine reduced the risk of COVID-19 hospitalization by 72% among immunocompetent adults without waning through 6 months postvaccination. After hospitalization for COVID-19, vaccinated immunocompetent patients were less likely to require IMV or die compared to unvaccinated immunocompetent patients.

Effectiveness of mRNA Vaccines Against COVID-19 Hospitalization by Age and Chronic Medical Conditions Burden Among Immunocompetent US Adults, March-August 2021.

Vaccine effectiveness (VE) against COVID-19 hospitalization was evaluated among immunocompetent adults (≥18 years) during March-August 2021 using a case-control design. Among 1669 hospitalized COVID-19 cases (11% fully vaccinated) and 1950 RT-PCR-negative controls (54% fully vaccinated), VE was 96% (95% confidence interval [CI], 93%-98%) among patients with no chronic medical conditions and 83% (95% CI, 76%-88%) among patients with ≥ 3 categories of conditions. VE was similar between those aged 18-64 years versus ≥65 years (P > .05). VE against severe COVID-19 was very high among adults without chronic conditions and lessened with increasing comorbidity burden.