(HealthDay News) — Vaccine effectiveness (VE) is high for preventing COVID-19-associated hospitalization, even during predominance of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) delta strain, according to two studies published in the Sept. 10 early-release issue of the U.S. Centers for Disease Control and Prevention Morbidity and Mortality Weekly Report.
Shaun J. Grannis, M.D., from the Regenstrief Institute in Indianapolis, and colleagues examined medical encounters from 187 hospitals and 221 emergency departments and urgent care clinics across nine states during June to August 2021. The researchers found that among adults hospitalized with COVID-19-like illness, SARS-CoV-2 infections were identified among 18.9% and 3.1% of unvaccinated and fully vaccinated patients, respectively. VE was 86% against COVID-19 hospitalization overall and was significantly lower among adults aged 75 years and older versus those aged 18 to 74 years (76% versus 89%). VE was highest for Moderna versus Pfizer-BioNTech and Janssen recipients across all ages (95% versus 80% and 60%, respectively). VE against COVID-19 emergency department/urgent care encounters was 82% overall and was highest for Moderna versus Pfizer-BioNTech and Janssen vaccine recipients (92% versus 77% and 65%, respectively).
Kristina L. Bajema, M.D., from the CDC COVID-19 Response Team, and colleagues examined mRNA VE against COVID-19-associated hospitalizations among 1,175 U.S. veterans aged 18 years or older at five Veterans Affairs Medical Centers during Feb. 1 to Aug. 6, 2021. The researchers found that the overall adjusted VE was 86.8% against COVID-19-associated hospitalization and was similar before and during delta prevalence (84.1% and 89.3% during Feb. 1 to June 30 and July 1 to Aug. 6, respectively). Among adults aged 65 years or older and those aged 18 to 64 years, VE was 79.8% and 95.1%, respectively.
“Additional evaluations, particularly among older adults with high prevalences of underlying conditions, are important to assess vaccine effectiveness in these populations,” Bajema and colleagues write.
