Study shows dramatic drop in effectiveness of three COVID-19 vaccines over time – .

Study shows dramatic drop in effectiveness of three COVID-19 vaccines over time – .

Syringes loaded with Johnson & Johnson vaccine lie in a tray at a mobile vaccination site in Miami. (Wilfredo Lee / Associated Press)

As the Delta variant has become the dominant strain of coronavirus across the United States, the three COVID-19 vaccines available to Americans have lost some of their protective power, with the vaccine’s effectiveness in a large group of dropping veterans. between 35% and 85%, according to a new study.

Researchers who searched the records of nearly 800,000 U.S. veterans found that in early March, as the Delta variant gained traction in U.S. communities, the three vaccines were roughly equal in capacity. prevent infections.

But over the next six months that changed dramatically.

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

The effectiveness of injections given by Pfizer and the BioNTech vaccine, which also used two doses, increased from 87% to 45% over the same period.

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

The results were published Thursday in the journal Science.

All three vaccines held up better in their ability to prevent deaths from COVID-19, but in July – as the Delta variant began to lead to a three-month wave of infections and deaths – the effectiveness of the shots on this score also revealed large discrepancies.

Among veterans 65 and older who were inoculated with the Moderna vaccine, those who developed a “breakthrough” infection were 76% less likely to die from COVID-19 than unvaccinated veterans of the same age.

Older veterans who received the Pfizer-BioNTech vaccine and subsequently suffered a breakthrough infection were 70% less likely to die than their unvaccinated peers.

And when older veterans who received a single injection of the J&J vaccine suffered a breakthrough infection, they were 52% less likely to die than their peers who received no injections.

For veterans under 65, the Pfizer-BioNTech and Moderna vaccines provided the best protection against a fatal case of COVID-19, at 84% and 82%, respectively. When young veterans inoculated with the J&J vaccine suffered a breakthrough infection, they were 73% less likely to die from COVID-19 than their unvaccinated peers.

Representatives for Johnson & Johnson did not immediately respond to requests to discuss the study results.

The Centers for Disease Control and Prevention has recommended booster shots for anyone who received the Johnson & Johnson vaccine at least two months earlier.

Boosters are also recommended six months after a second dose of Moderna or Pfizer vaccines for all people 65 years of age and older; those who have health problems that make them more vulnerable to a severe case of COVID-19; those who live in nursing homes or other group settings; and those who live or work in high risk settings such as hospitals or prisons.

In addition, all people with weakened immune systems are advised to be vaccinated if it has been at least 28 days since their vaccine has had full effect.

With millions of vaccinated Americans wondering if they need a boost, the new study offers the most comprehensive comparison to date of the performance of the three vaccines across the country this year.

He followed 780,225 veterans of the United States Armed Forces from February 1 to October 1. Almost 500,000 of them had been vaccinated, while just under 300,000 had not.

Coming from across the country, all were taken care of by the Unified Veterans Affairs System, which provides health care to 2.7% of the American population. While the study group was ethnically and racially diverse, the record keeping that the researchers relied on was consistent.

As they were veterans, the study population included six times more men than women. And they were 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 in vaccine protection against disease and death was seen in both young and old.

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

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

Strong evidence for declining vaccine potency should prompt even states and localities with highly vaccinated populations to consider retaining mask warrants, the authors said. And the results strongly support the CDC’s recent recommendation that all J&J vaccine recipients be boosted.

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

Other researchers have found similar evidence of a decrease in the effectiveness of the vaccine. But they suggested that the immune system’s defenses against SARS-CoV-2 simply wane over time, and that the vaccine’s waning efficacy would likely have been seen with or without the arrival of a new, more transmissible strain. .

This story originally appeared in the Los Angeles Times.


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