Multiple studies support efficacy of Moderna's COVID-19 vaccine
The Moderna vaccine was found to be more effective than the Pfizer-BioNTech vaccine at preventing symptomatic COVID-19 in U.S. health care workers, according to findings published in The New England Journal of Medicine.
However, both mRNA vaccines were highly effective, Tamara Pilishvili, PhD, MPH, an epidemiologist in the COVID-19 response team at the CDC, and colleagues wrote.
“Our study adds to the literature by focusing on vaccine effectiveness among groups who are more at risk for severe COVID-19 illness due to their occupation or presence of underlying conditions,” Pilishvili told Healio Primary Care.
She stressed that the CDC “does not recommend one authorized vaccine brand over another and encourages all individuals to not wait for a specific brand to get vaccinated.”
Pilishvili and colleagues evaluated both vaccines’ effectiveness in a real-world setting. They conducted a test-negative, case-control study of 1,482 health care workers who had received positive PCR or antigen-based test results for SARS-CoV-2 and displayed at least one COVID-19 symptom and a control group comprising 3,449 workers who received negative PCR test results for SARS-CoV-2. Participants were enrolled from Dec. 28, 2020, through May 19, 2021, at 33 sites in 25 states; 68% of the facilities included in the study were acute care hospitals and 32% were long-term care facilities.
The facilities began administering COVID-19 vaccine doses to staff in December 2020. During the study period, vaccine coverage among health care workers ranged from 55% to 98% for at least one vaccine dose and 51% to 94% for both vaccine doses.
The researchers found that vaccine effectiveness for those who were partially vaccinated was 88.9% among participants who received the Moderna vaccine (95% CI, 84.6-91.8) and 77.6% among those who received the Pfizer-BioNTech vaccine (95% CI, 70.9-82.7). Effectiveness increased in those who were fully vaccinated, to 96.3% with the Moderna vaccine (95% CI, 91.3-98.4) and 88.8% with the Pfizer-BioNTech vaccine (95% CI, 84.6-91.8). Overall, vaccine effectiveness was consistent despite variations in participants’ racial/ethnic identities, underlying conditions, the level of patient contact and age, according to Pilishvili and colleagues, However, vaccine effectiveness was estimated to be lower during weeks 9 to 14 after participants’ second dose compared with weeks 3 to 8, although the “confidence intervals overlapped widely,” they wrote.
“The effectiveness of Moderna and Pfizer vaccines in this study was evaluated by comparing persons vaccinated with each vaccine to unvaccinated individuals. The study was not designed to compare effectiveness of one vaccine to the other,” Pilishvili said. “The study did demonstrate that a full two-dose regimen of either of the two mRNA vaccines is highly effective in preventing symptomatic illness.”
While the findings show that both the Moderna and Pfizer-BioNTech vaccines were “highly effective” at preventing symptomatic COVID-19, additional research is required to ascertain the long-term duration of protection and the effectiveness against emerging variants, according to Pilishvili and colleagues.
“The study [by Pilishvili and colleagues] found that both vaccines were highly effective, but since they were not studied head-to-head in a randomized controlled trial, where unmeasured sources of potential confounding could be limited (eg differences in vaccine recipient conditions like age, underlying conditions, local prevalence of delta variant, etc.), one could not make a statement about relative superiority between vaccines based on these data,” Kenneth H. Mayer, MD, medical research director at Fenway Health in Boston, told Healio Primary Care.
More findings show high efficacy of Moderna vaccine
A separate study published in The New England Journal of Medicine provided more evidence of the efficacy of the Moderna vaccine. In the phase 3, observer-blinded, placebo-controlled COVE trial, Hana M. El Sahly, MD, professor of molecular virology and microbiology and infectious diseases at Baylor College of Medicine, and colleagues found that it was 93.2% effective (95% CI, 91%-94.8%) at preventing illness and 98.2% effective (95% CI, 92.8%-99.6%) at preventing severe disease at more than 5 months following the second dose in a cohort of healthy volunteers who were at high risk for COVID-19 or its complications. The study included more than 30,000 participants — 15,209 who received the Moderna vaccine and 15,206 who received placebo between July 27 and Oct. 3, 2020. According to the researchers, more than 96% of participants received both doses. The Moderna vaccine also exhibited an “acceptable safety profile” and protected against asymptomatic infection, according to El Sahly and colleagues.
Separate findings from a case-control analysis published in MMWR by Wesley H. Self, MD, associate professor at the Vanderbilt University School of Medicine, and colleagues compared the Moderna, Pfizer-BioNTech and Johnson & Johnson vaccines for effectiveness against COVID-19. The Moderna vaccinate exhibited the highest efficacy against hospitalization in U.S. adults without immunosuppressing conditions at 93% (95% CI, 91%-95%), compared with 88% from Pfizer-BioNTech vaccine (95% CI, 85%-91%) and 71% from the Johnson & Johnson vaccine (95% CI, 56%-81%).
However, the delta variant may dampen vaccine effectiveness. In a recent report published in MMWR, researchers examined the effectiveness of all three available COVID-19 vaccines, which had dropped from 91% (95% CI, 81%-96%) to 66% (95% CI, 26%-84%) in U.S. health care workers once the delta variant became the predominant cause of SARS-CoV-2 infections.
“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 U.S. and worldwide,” Sahly and colleagues wrote.