August 13, 2021: -The risk of suffering a breakthrough COVID-19 infection with the delta variant after being fully vaccinated with the Moderna vaccine may be much less than the risk for those receiving the Pfizer vaccine, according to a new Mayo Clinic study that is waiting for a full review.

In July, the study found that in Florida, where COVID cases are at an all-time high and the delta variant is prevalent, the breakthrough case risk was nearly 60% lower for Moderna recipients than Pfizer recipients.

Similarly, in Minnesota, the authors found that the Moderna vaccine was 76% effective in preventing infection, but the Pfizer vaccine (known as BNT162b2) was effective by 42%.

“Comparing rates of the infection amid matched individuals fully vaccinated with mRNA-1273 versus BNT162b2 across Mayo Clinic Health System sites in multiple states, -1273 conferred a two-fold risk reduction against breakthrough infection compared to BNT162b2,” the authors wrote in their abstract.

To be sure, the authors found that both the vaccines “strongly protect” against severe disease; the difference appears to be about whether people get infected at all in the first place. The CDC has said the risk of infection is 8x higher in the unvaccinated than the people who are vaccinated, and the risk of hospitalization or death is 25x higher.

On Sunday, the pre-print study was first released, which has not gone through a peer review or been published in an academic journal. However, it gained more notice when Axios reported that the Biden administration took the data as a “wake-up call.”

Pfizer told Axios that it and partner BioNTech “expect to be able to develop and produce a tailor-made vaccine against that variant in approximately 100 days after a decision to do so, subject to regulatory approval.”

In a subsequent statement, the company affirmed the effectiveness of its vaccines and said it was committed to developing boosters as well.

The previous week, Moderna warned that breakthrough infections were rising and said those who received its vaccine would likely need a booster dose before winter. And late last month, Pfizer said a booster in testing would be effective against the delta variant.

Data from New Jersey, the delta now accounts for 90% of all positive COVID samples tested. This week underscores the key points: Breakthrough infections still account for a tiny share of new COVID hospitalizations, but that share has increased significantly in the last few weeks.

Fully vaccinated New Jerseyans accounted for 18.5% of all new COVID cases on July 20-26.

Pfizer accounts for 30% of over 10.6 million vaccine doses administered in New Jersey to date, while Moderna accounts for nearly 21%, state data shows.