Current Covid shots provide a high level of protection against hospitalization and death, according to a summary of the efficacy of eight vaccines that showed the Pfizer Inc.-BioNTech SE jab may better at stopping at least two worrisome coronavirus variants.
Efficacy against Covid-linked disease averaged about 85% after a full course, rising to almost 100% protection against severe disease, hospitalization or death, Julia Shapiro, Natalie Dean, Ira Longini and colleagues said in a paper released Friday before peer-review and publication. The University of Florida researchers compared data from journal articles and media reports for products that have gone through double-blinded, placebo-controlled, late-stage vaccine trials, as well as observational studies.
"These estimates should be useful for constructing mathematical models for vaccination impact and for making policy decisions involving vaccination," they said. They plan to update their research, which received funding from the U.S. National Institutes of Health, as more information becomes available.
The unprecedented speed with which safe and effective vaccines have been developed and rolled out across the world have enabled many economies to reopen, paving the way for a recovery from the worst pandemic in a century. Still, uncontrolled spread of the SARS-CoV-2 virus risks spawning new variants that may undermine the potency of these immunizations.
Protection against any disease with infection for three so-called variants of concern averaged 86% for the B.1.1.7 strain first detected in the U.K., 61% for the P.1 strain that drove an explosive outbreak in Brazil, and 56% for the B.1.351 strain discovered in South Africa, the University of Florida researchers said.
Vaccine efficacy was estimated for immunizations that are being rolled out on local and global scales, they said. These include the Pfizer, Moderna Inc., Johnson & Johnson, AstraZeneca Plc, "Sputnik", Novavax Inc., Sinovac Biotech Ltd., and Sinopharm Group Co. products.
"Some of the estimates are based on rigorous, preplanned statistical analyses from double-blinded, placebo-controlled trials, while others are extracted from observational studies with different levels of control," the researchers said.
Vaccine efficacy to prevent any Covid-caused disease after two doses is summarized below:
The researchers found vaccine efficacy against infectiousness was 54%, on average, indicating immunization reduces the direct transmission of SARS-CoV-2 to others by 54%. Data for four vaccines are summarized below.
Estimates for vaccine efficacy for three variants of concern are summarized below. The researchers found B.1.1.7 led to "somewhat reduced" efficacy compared with the "wild type" strain. In contrast, the P.1 and B.1.351 variants led to considerably lower vaccine efficacy, owing to mutations that affect immune function.
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