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In a new study, both messenger RNA vaccines available in the U.S. demonstrated high effectiveness against COVID-19, although the Moderna vaccine was associated with a lower risk for infection and hospitalization than the Pfizer-BioNTech vaccine. The trial is the “first head-to-head comparison of the effectiveness” of each vaccine, according to a press release. “Given the high effectiveness of both the Moderna and Pfizer vaccines, confirmed by our study, either one is recommended to any individual offered a choice between the two,” Barbra A. Dickerman, PhD, a study author and an epidemiology instructor with the Harvard T.H. Chan School of Public Health, said in a press release. “While the estimated differences in effectiveness were small on an absolute scale, they may be meaningful when considering the large population scale at which these vaccines are deployed.” For the study, Dickerman and colleagues analyzed the electronic health records of nearly 440,000 U.S. veterans who were administered either vaccine (219,842 in each group) between Jan. 4 and May 14. The participants were matched in a 1:1 ratio based on their risk factors and followed for up to 24 weeks. “The two vaccine groups were extremely similar in terms of variables with respect to an extensive set of demographic, geographic and health-related attributes,” Dickerman said in the release.
The results, published in The New England Journal of Medicine, showed that the estimated risk for documented SARS-CoV-2 infection was 5.75 events per 1,000 persons (95% CI, 5.39-6.23) in the Pfizer-BioNTech cohort and 4.52 events per 1,000 persons (95% CI, 4.17-4.84) in the Moderna cohort. During a period in which alpha was the predominant variant, the excess number of events per 1,000 persons for Pfizer compared with Moderna was 1.23 (95% CI, 0.72-1.81) for documented infection, 0.44 (95% CI, 0.25-0.7) for symptomatic infection, 0.55 (95% CI, 0.36-0.83) for COVID-19-related hospitalization, 0.1 (95% CI, 0-0.26) for COVID-19-related ICU admission and 0.02 (95% CI, 0.06 to 0.12) for death from COVID-19. The corresponding excess risk with Pfizer vs. Moderna for documented infection during a 12-week period in which delta was the predominant variant was 6.54 events per 1,000 persons (95% CI, 2.58 to 11.82). J.P. Casas, MD, PhD, a study co-author and associate epidemiologist at Brigham and Women's Hospital, noted in the press release that the findings were consistent “regardless of the predominant strain.”
In a related editorial, Eric J. Rubin, MD, PhD, the editor-in-chief of The New England Journal of Medicine, and Dan L. Longo, MD, a professor of medicine at Harvard Medical School, said the take-home message “is not about differences — it’s about similarities.” “We are lucky to have such good options,” they wrote. “Vaccination with any vaccine is far better than remaining unprotected. The message is that the best vaccine is the one that’s available.”
Original findings published in New England J. Medicine (Dec. 1, 2021):
