What Is the Effectiveness of Vaccines? A Study from the USA

According to a report by the National Center for Disease Control and Prevention, the most effective COVID-19 vaccine authorized for emergency use by the U.S. Food and Drug Administration is Moderna.

To assess the effectiveness of the Moderna, Pfizer, and Janssen vaccines in preventing hospitalizations due to COVID-19, the CDC conducted a case-control study from March 11 to August 15, 2021, among 3,689 individuals aged 18 and older hospitalized at 21 hospitals in 18 U.S. states.

The research conducted in the 21 hospitals in the U.S. indicated that the two-dose regimens of the mRNA vaccines, Moderna and Pfizer, provide high effectiveness in preventing hospitalizations caused by COVID-19, with respective effectiveness rates of 93% and 88%, while Janssen's vaccine showed an effectiveness rate of 71%.

Despite some variability in the levels of protection indicated by the data, the COVID-19 vaccines authorized by the Food and Drug Administration do provide significant protection against hospitalizations due to COVID-19.

The effectiveness of the Pfizer vaccine in preventing COVID-19-related hospitalizations is lower than that of the Moderna vaccine, which may be due to the higher RNA content in the Moderna vaccine, differences in the timing of doses (3 weeks for Pfizer and 4 weeks for Moderna), or possible variations between the groups involved in the vaccinations.