As the Delta variant became the dominant strain of the coronavirus in the United States, all three COVID-19 vaccines available to Americans have lost some of their protective power, with the vaccine’s effectiveness among a large group of veterans dropping between 35% and 85%, according to a new study.
Researchers who sifted through the records of nearly 800,000 U.S. veterans found that in early March, just as the Delta variant was gaining momentum among American communities, the three vaccines were roughly equal in their ability to prevent infections.
But in the next six months, things changed dramatically.
At the end of September, Moderna’s two-dose COVID-19 vaccine, measured as 89% effective in March, was only 58% effective.
The effectiveness of injections made by Pfizer and BioNTech, which also used two doses, dropped from 87% to 45% over the same period.
And most surprisingly, the protective power of Johnson & Johnson’s single-dose vaccine dropped from 86% to just 13% in those six months.
The discoveries were published Thursday in the journal Science.
The three vaccines held up best in their ability to prevent deaths from COVID-19, but in July – when the Delta variant began to drive a three-month surge in infections and deaths – the effectiveness of hits on that score had also revealed large gaps.
Among veterans aged 65 and over who were inoculated with the Moderna vaccine, those who developed a so-called 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 had a breakthrough infection were 70 percent less likely to die than their unvaccinated peers.
And when older vets 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 did not receive any vaccines.
For veterans under the age of 65, Pfizer-BioNTech and Moderna vaccines provided the best protection against a fatal case of COVID-19, at 84% and 82%, respectively. When younger 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.
Johnson & Johnson representatives did not immediately respond to requests to discuss the study results.
The Centers for Disease Control and Prevention have recommended booster shots for all who received the Johnson & Johnson vaccine at least two months before.
Boosters are also recommended six months after a second dose of Moderna or Pfizer vaccines for anyone aged 65 and over; those with medical conditions that make them more vulnerable to a severe case of COVID-19; those living 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 compromised immune systems are advised to undergo a booster injection if it has been at least 28 days since the vaccine took full effect.
With millions of vaccinated Americans assessing whether they need a boost, the new study offers the most comprehensive comparison of how the three vaccines have worked nationwide this year.
It monitored 780,225 US military veterans from February 1 to October 24. 1. Nearly 500,000 of them had been vaccinated, while just under 300,000 were not.
Hailing from across the country, all have been cared for by the Department of Veterans Affairs’ unified system, which provides health care to 2.7% of the US population. While the study group was ethnically and racially diverse, the record keeping on which the researchers relied was uniform.
Since they were veterans, the study population comprised six times more men than women. And they distorted the elderly: about 48% were 65 or older, 29% were between 50 and 64, and 24% were under the age of 50.
Although older veterans were more likely to die than younger veterinarians during the study period, the decline in vaccine protection against disease and death was observed in both the young and the elderly.
The study was conducted by a team from the Public Health Institute of Oakland, the Veterans Affairs Medical Center of San Francisco and the University of Texas Health Science Center.
Dr. Barbara Cohn, the study’s lead author said, in addition to comparing COVID-19 vaccines, the team’s analysis provides “a lens for making informed decisions about primary vaccination, boosters and other multiple levels of protection.” This includes mask mandates, coronavirus testing, and other public health measures aimed at thwarting viral spread.
Strong evidence of the declining power of vaccines should also prompt states and localities with highly vaccinated populations to consider maintaining the mandates of the masks, the authors said. And the findings strongly support the CDC’s recent recommendation that all J&J vaccine recipients receive a booster.
The study concluded that the Delta variant, which caused a wave of infections and deaths across the country during the spring and summer, was probably the factor that most eroded vaccine protection.
Other researchers have found similar evidence the decrease in the effectiveness of the vaccine. But they suggested that the immune system’s defenses against SARS-CoV-2 simply wane with time and that the declining vaccine efficacy would likely be seen with or without the arrival of a new one. most transmissible strain.