Aug 12 2021

Mayo Study: Vaccines Significantly Less Effective in July

Delta Variant Surge Challenges Vaccines

A study published in medRxiv indicates mRNA vaccines’ efficacy against infection—particularly the Pfizer-BioNTech vaccine—has dropped significantly since the delta variant became widespread in July.  The hospitalized patients reported in the study were in the Mayo system and affiliated hospitals in Arizona, Florida, Iowa, Minnesota, and Wisconsin.

Specifically, the researchers found that during July, the Moderna vaccine appeared to have an estimated efficacy of 76% against infection, while the Pfizer-BioNTech vaccine had an estimated efficacy of 42% against infection.

Both vaccines had similar 21-day hospitalization rates, 21-day ICU admission rates, and 28-day mortality rates.

Venky Soundararajan, a lead author on the study, said based on the data compiled so far, the vaccines’ reduced efficacy likely stems from “a combination” of both reduced efficacy over time and reduced efficacy against the delta variant. “The Moderna vaccine is likely—very likely—more effective than the Pfizer vaccine in areas where delta is the dominant strain, and the Pfizer vaccine appears to have a lower durability of effectiveness.”

medRxiv Advisory Board Daily Briefing 8/11/21

Read the complete announcement here.

See July 29 PCA vaccine article here


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