(HealthDay News) — At more than five months, the mRNA-1273 vaccine continues to be efficacious for preventing COVID-19 and severe COVID-19, according to a study published online Sept. 22 in the New England Journal of Medicine.
Hana M. El Sahly, M.D., from the Baylor College of Medicine in Houston, and colleagues enrolled volunteers at high risk for COVID-19 or its complications and randomly assigned them to receive two intramuscular injections of mRNA-1273 or placebo, 28 days apart, at 99 centers. A total of 30,415 participants were enrolled: 15,209 and 15,206 were randomly assigned to receive the vaccine and placebo, respectively.
Median follow-up was 5.3 months in the blinded phase. The researchers found that vaccine efficacy was 93.2 percent for preventing COVID-19 illness, with 55 and 744 confirmed cases in the mRNA-1273 and placebo groups, respectively (9.6 and 136.6 confirmed cases per 1,000 person-years).
The efficacy was 98.2 percent for preventing severe disease, with two and 106 cases in the mRNA-1273 and placebo groups, respectively. The efficacy was 63.0 percent for preventing asymptomatic infection starting 14 days after the second injection, with 214 and 498 cases in the mRNA-1273 and placebo groups, respectively.
Across ethnic and racial groups, age groups, and participants with coexisting conditions, the investigators found vaccine efficacy to be consistent.
“The interplay of viral evolution with vaccine distribution in the next months will determine the trajectory of the pandemic, which continues to evade predictions and shape much of the social and economic life in the United States and worldwide,” the authors write.
Several authors disclosed financial ties to pharmaceutical companies, including Moderna, the manufacturer of the mRNA-1273 vaccine.