Nicole DeFeudis
Editor
A study of patients in the Mayo Clinic Health System across multiple states suggests those who received Pfizer’s Covid-19 vaccine are at two-fold higher risk of breakthrough infection compared to those who got the Moderna vaccine.
It’s important to note that the study, published Sunday in the preprint server medRxiv, has not been peer-reviewed.
The study began in Minnesota, where researchers have been analyzing the efficacy of the vaccines on a monthly basis since February 2021. As cases increased in July and the Delta variant became more prominent, the scientists measured a 76% efficacy against infection for the Moderna vaccine and a 42% efficacy against infection for Pfizer’s. Those rates are much lower than the figures seen through April 2021 (93.3% for Moderna and 86.1% for Pfizer).
The ability of the vaccines to prevent hospitalization has remained “more consistently high,” according to the researchers. Both had similar rates of ICU admission and complications.
To validate the findings, the scientists compared breakthrough infection rates in other states in the Mayo Clinic Health System, including Wisconsin, Arizona, Florida, and Iowa. In most states, those who received the Moderna vaccine were less likely to experience a breakthrough infection, according to the study.
“Considering all states together, mRNA-1273 conferred a two-fold risk reduction against breakthrough infection compared to BNT162b2,” researchers said.
They added:
mRNA-1273 and BNT162b2 were originally designed, tested, and proven to reduce the burden of symptomatic disease, hospitalization, and death related to SARS-CoV-2 infection. This study further supports the effectiveness of both vaccines in doing so, even despite the evolution of more transmissible viral variants.
Pfizer said last month that it’s likely a third dose may be needed within six to 12 months after full vaccination. While protection against severe disease remains high, a decline in efficacy against symptomatic disease and the emergence of new variants are expected, the company said in a statement.
Pentagon looks to require vaccines for members of the military. The Pentagon has said it will look to make the Covid-19 vaccine mandatory for military members next month.
Defense Secretary Lloyd Austin will request that President Biden make the vaccine a requirement in September, by which time the shots could have full regulatory approval, Pentagon press secretary John Kirby said Monday.
“I strongly support Secretary Austin’s message to the Force today on the Department of Defense’s plan to add the COVID-19 vaccine to the list of required vaccinations for our service members not later than mid-September,” Biden responded.
So far, more than 73% of active duty personnel have received at least one shot, according to Kirby.
“You can consider this memo, not just a warning order to the services, but to the troops themselves,” he said.
The news comes as large companies — including Walmart, Disney, United Airlines, and Pfizer — move to require the vaccines for some employees. The Department of Justice has ruled that such mandates are legal, even for Covid-19 vaccines that have not yet been fully approved, and remain subject to emergency use authorizations.
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