In the first direct comparison of the efficacy of Pfizer-BioNTech and the Moderna COVID-19 vaccines, researchers examined the electronic health records of veterans who had received each vaccine. Both vaccines were extremely effective in preventing COVID-19 outcomes such as documented infection, hospitalization, and death.
However, the Moderna vaccine was found to offer an increased level of protection, including a 21% lower risk of documented infection and a 41% lower risk of hospitalization, according to the research team, whose results were published on December 1, 2021, in New England Journal of Medicine.
“Both vaccines are incredibly effective, with only rare breakthrough cases,” said Dr. JP Casas, a member of the research team of experts from the U.S. Department of Veterans Affairs (VA), Harvard TH Chan School of Public Health, and Brigham and Women’s Hospital. “But regardless of the predominant tribe – Alpha earlier and then Delta later – Moderna has proven to be a little more effective,” said Casas, an epidemiologist and associate professor at Brigham and Women’s Hospital and Harvard Medical School and executive director of VA’s Million Veteran Program for genetics and health research.
Researchers designed their comparative efficacy study to address the previously unanswered question of which of the two mRNA vaccines is most effective. Efficacy was measured in terms of five COVID-related outcomes: documented COVID-19, symptomatic illness, hospitalization, intensive care unit, and death. Investigators relied on the electronic health records of U.S. veterans who received one of the two COVID-19 vaccines between early January 2021 and mid-May 2021.
As originally designed, the research focused on the Alpha variant that was prevalent at the time. The study matched 219,842 recipients of the Pfizer vaccine to the same number of recipients of the Moderna vaccine. The two groups were matched based on a number of clinical and demographic factors that could influence the results.
During the study’s 24-week follow-up period, the estimated risk of documented infection was 4.52 events per day. 1,000 people in the Moderna vaccine group and 5.75 per. 1,000 in the Pfizer group. This represents a surplus of 1.23 cases of documented infection per. 1,000 people in the Pfizer group. Investigators also observed an excess of symptomatic COVID-19 (0.44 incidents), hospitalization (0.55 incidents), ICU hospitalization (0.10 incidents), and death (0.02 incidents) per day. 1,000 people in the Pfizer group compared to the Moderna group, but these differences were smaller.
This pattern with a lower risk for Moderna persisted in an additional phase of research that covered a time frame with Delta as the mainstay. In this comparison, the excess risk of documented infection over 12 weeks was 6.54 events per week. 1,000 people for the Pfizer vaccine compared to Moderna. Given the shorter time frame available for this supplementary research, infection was the only outcome that researchers analyzed. The estimates were also considered less accurate because a smaller number of individuals were eligible for this analysis.
Randomized trials comparing mRNA vaccines to placebos had previously shown that both vaccines were highly effective against symptomatic COVID-19 infection (95% efficacy for Pfizer-BioNTech, 94% for Moderna), and similar benefits were observed with vaccine use. in the real world.
“Given the high efficacy of both the Moderna and Pfizer vaccines, confirmed by our study, each of them is recommended for any person offered a choice between the two,” said the study’s lead author, Dr. Barbra A. Dickerman, an epidemiological instructor with the Harvard TH Chan School of Public Health. “However, although the estimated differences in efficacy were small on an absolute scale, they can be meaningful when considering the large population scale in which these vaccines are used. This information may be useful to larger decision – making bodies.”
The expansive VA registration system, which covers millions of patients nationwide, supported a very large sample size. This in turn allowed the study to identify even small differences in efficacy between the Pfizer and Moderna vaccines. The researchers used a method known as causal inference to reflect a randomized trial – the gold standard in health research – as closely as possible. Causal inference is a type of data analysis that helps researchers draw firm conclusions about cause and effect.
Experts on causation on the research team included Dickerman and Dr. Miguel A. Hernán, professor of biostatistics and epidemiology at the Harvard School of Public Health and director of the school’s CAUSALab. Dickerman, Hernán and Casas lead the methodological core of VA-CAUSAL, a VA-Harvard partnership focusing on the development of new methods for causal inference in research.
A primary challenge for this research was to ensure that the vaccine groups studied were comparable in terms of properties other than the vaccine received that could predict infection or the severity of the disease. The VA databases allowed researchers to accurately characterize recipients of each vaccine type and closely match them in terms of age, gender, race, geographic location, and other traits that could influence COVID-19-related outcomes.
“After this careful matching, we found that the two vaccine groups were extremely similar in terms of variables in terms of a comprehensive set of demographic, geographic, and health-related characteristics,” Dickerman said. “This allowed our observational analysis to produce exceptionally credible results during a global emergency where rapid responses are needed and randomized trials may be impractical.”
As the global pandemic continues to unfold, the research team is working on responses related to the comparative security, versus the efficacy of the Pfizer and Moderna vaccines. Dickerman characterizes comparative safety as an “additional piece of the puzzle to support vaccine decision-making.”
Even beyond this analysis, there is a need for further evaluation of the comparative efficacy and safety of vaccines, the authors concluded in their New England Journal of Medicine Article. Meanwhile, given the evidence already collected, the authors concluded about the Pfizer and Moderna vaccines considered in their study, “Given the high efficacy and safety profile of both mRNA vaccines, each of them is highly recommended. ”
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Barbra A. Dickerman et al., Comparative efficacy of BNT162b2 and mRNA-1273 vaccines in American veterans, New England Journal of Medicine (2021). DOI: 10.1056 / NEJMoa2115463
Provided by Veterans Affairs Research Communications
Citation: Researchers perform first head-to-head comparison of Pfizer and Moderna vaccines (2021, December 2) retrieved December 2, 2021 from https://medicalxpress.com/news/2021-12-head-to- head-comparison -pfizer-modern-vaccines.html
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