The first study was published by medRxiv “The Preprint Server for Health Sciences” on August 9th, and compared (on 25,589 vaccinated v.
25,589 unvaccinated Minnesotans) “the effectiveness of two full-length Spike protein-encoding mRNA vaccines from Moderna
(mRNA-1273) and Pfizer/BioNTech (BNT162b2) in the Mayo Clinic Health System in Minnesota over time from January to July
2021.” Moderna was 86% effective against the infection; Pfizer was 76% effective. In July (when the “Delta” variant
first became dominant) Moderna was 91.6% effective against hospitalization; Pfizer was 85%. But during that month,
effectiveness against the infection was 76% for Moderna v. 42% for Pfizer. Nationwide (including Mayo in MN, WI, AZ, FL, & IA), Moderna was about twice as effective “against breakthrough infection” v. Pfizer.
The second study was far smaller, published on September 10th by the CDC, and studied only 1,175 hospitalized U.S. veterans (93% male)
at V.A. centers nationwide. Moderna was estimated at 91.6% effective, Pfizer at 83.4%. Since no non-hospitalized
comparison-sample were studied, “Vaccine effectiveness … to prevent Covid-19-associated hospitalization was estimated by
using multivariate logistic regression to compare the odds of full vaccination between case-patients and controls,” and
so the reliability of this study was far less than in the Mayo Clinic study.
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Investigative historian Eric Zuesse is the author of They’re Not Even Close: The Democratic vs. Republican Economic Records, 1910-2010, and of CHRIST’S VENTRILOQUISTS: The Event that Created Christianity.