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LATimes: Study Shows Dramatic Decline in Effectiveness of all Three COVID-19 Vaccines Over Time

A study published in Science from PHI, the Veterans Affairs Medical Center and the University of Texas Health Science Center found that all three COVID-19 vaccines lost some of their protective power as the Delta variant was surging. PHI’s Dr. Barbara Cohn, the study’s lead author, comments on the significance of the findings for decision-making around the ongoing need for public health measures aimed at countering the spread of COVID-19.

  • Los Angeles Times
a blue-gloved hand holding a vial of Janssen COVID-19 vaccine

As the Delta variant became the dominant strain of coronavirus across the United States, all three COVID-19 vaccines available to Americans lost some of their protective power, with vaccine efficacy among a large group of veterans dropping between 35% and 85%, according to a new study.

Researchers who scoured the records of nearly 800,000 U.S. veterans found that in early March, just as the Delta variant was gaining a toehold across American communities, the three vaccines were roughly equal in their ability to prevent infections.

But over the next six months, that changed dramatically.

By the end of September, Moderna’s two-dose COVID-19 vaccine, measured as 89% effective in March, was only 58% effective.

The effectiveness of shots made by Pfizer and BioNTech vaccine, which also employed two doses, fell from 87% to 45% in the same period.

And most strikingly, the protective power of Johnson & Johnson’s single-dose vaccine plunged from 86% to just 13% over those six months.

The findings were published Thursday in the journal Science.

The study was conducted by a team from the Public Health Institute in Oakland, the Veterans Affairs Medical Center in San Francisco, and the University of Texas Health Science Center.

Dr. Barbara Cohn, the study’s lead author, said in addition to its comparison of COVID-19 vaccines, the group’s analysis provides “a lens for making informed decisions around primary vaccination, booster shots, and other multiple layers of protection.” That includes mask mandates, coronavirus testing and other public health measures aimed at countering viral spread.

Strong evidence of the vaccines’ declining power should prompt even states and locales with highly vaccinated populations to consider retaining mask mandates, the authors said. And the findings strongly support the CDC’s recent recommendation that all recipients of the J&J vaccine get a booster.

The study concluded that the Delta variant, which drove a wave of infections and deaths across the country this spring and summer, was likely the factor that most eroded the protection of vaccines.

The study tracked 780,225 veterans of the U.S. armed forces from Feb. 1 to Oct. 1. Close to 500,000 of them had been vaccinated, while just under 300,000 had not.

Hailing from across the country, all were cared for by the Veterans Affairs’ unified system, which provides healthcare to 2.7% of the U.S. population. While the group under study was ethnically and racially diverse, the record-keeping that researchers relied upon was uniform.

Because these were veterans, the study population comprised six times as many men as women. And they skewed older: about 48% were 65 or older, 29% were between 50 and 64, and 24% were under 50.

While older veterans were more likely to die than younger vets throughout the study period, the decline of the vaccines’ protection against illness and death was seen in both young and old.

Read the full story in the Los Angeles Times.

See more coverage of the study:

Originally published by Los Angeles Times


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