Study: Moderna COVID-19 Vaccine Demonstrates Superior Protection to Pfizer Vaccine


Moderna COVID-19 vaccine found to offer an increased level of protection, including a 21% reduced risk of documented infection and 41% lower risk of hospitalization.

Although both the Pfizer-BioNTech and Moderna COVID-19 vaccines are highly effective in preventing documented infection, hospitalization, and death, the Moderna vaccine provides an increased level of protection, according to a study published in the New England Journal of Medicine. The investigators said this was the first head-to-head comparison of the efficacy of the vaccines, examining health records of veterans who had received 1 of the 2 vaccines.

“Both vaccines are incredibly effective, with only rare breakthrough cases,” said J.P. Casas, MD, PhD, epidemiologist and associate professor with Brigham and Women’s Hospital and Harvard Medical School and executive director of the VA’s Million Veteran Program for genetics and health research, in a press release. “But regardless of the predominant strain—Alpha earlier and then Delta later—Moderna was shown to be slightly more effective.”

The study was designed to address the question of which mRNA vaccine is more effective. Investigators matched 219,842 recipients of the Pfizer vaccine to the same number of recipients of the Moderna vaccine, using a number of clinical and demographic factors that could potentially influence outcomes. Efficacy was measured through 5 COVID-19-related outcomes: documented COVID-19, symptomatic disease, hospitalization, ICU admission, and death.

According to the investigators, the Moderna vaccine was found to offer an increased level of protection, including a 21% lower risk of documented infection and 41% lower risk of hospitalization. The estimated risk of documented infection was 4.52 events per 1000 individuals in the Moderna vaccine group and 5.75 per 1000 in the Pfizer group across the study’s initial 24-week follow-up period, representing an excess of 1.23 cases of documented infection per 1000 people in the Pfizer group.

This pattern of lower risk was consistent during an additional research phase covering a time frame in which the Delta variant was the primary strain. Excess risk of documented infection over this 12-week comparison was 6.54 events per 1000 individuals compared to Moderna.

“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 2,” said Barbra A. Dickerman, PhD, an epidemiology instructor with the Harvard T.H. Chan School of Public Health. “However, 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. This information may be helpful for larger decision-making bodies.”

Excesses of symptomatic COVID-19, hospitalization, ICU admission, and death per 1000 individuals were observed in the Pfizer arm, though these differences were smaller and considered less significant by the investigators.


Which COVID-19 vaccine works better? [news release]. EurekAlert; December 1, 2021. Accessed December 3, 2021.

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