The results of two non-peer-reviewed studies released Sunday suggest that the Moderna COVID-19 vaccine may be more effective against the delta variant of the coronavirus than the Pfizer/BioNTech shot.
In a study of 50,000 people in the Mayo Clinic Health System, researchers said the effectiveness of the Moderna vaccine fell to 76% in July, from a high of 86% in early 2021.
The Pfizer vaccine’s effectiveness dropped from 76% to 42% during the same period.
The study examined adults in the Mayo Clinic Health System in Minnesota, Arizona, Florida, Iowa, and Wisconsin who received at least one dose of Pfizer or Moderna vaccine after Dec. 1, 2020 but before July 29, 2021.
According to the study’s authors, breakthrough infections were less likely among those who had the Moderna vaccine versus those who had the Pfizer shot. The rate of hospitalization was lower among those vaccinated with Moderna compared with Pfizer, as well.
When it came to those who had to be admitted to the ICU because of COVID-19 complications, the rate for both vaccines was comparable.
In a second study, nursing home residents in Ontario, Canada, showed a stronger immune response after receiving the Moderna vaccine than after the Pfizer/BioNTech vaccine.
Anne-Claude Gingras of the Lunenfeld-Tanenbaum Research Institute in Toronto, who led the Canadian study, said it is possible that the elderly may need higher vaccine doses, boosters, and other preventative measures, Reuters reported.
While the research showed a drop in effectiveness, the researchers who conducted the studies emphasized that both mRNA vaccines were highly effective at preventing hospitalization and deaths due to the virus.
The results of the studies show that a booster shot of one of the mRNA vaccines may be required for better protection against variants of the disease.
A Pfizer spokesperson told Reuters that “We continue to believe... a third dose booster may be needed within 6 to 12 months after full vaccination to maintain the highest levels of protection.”
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