Even if they get breakthrough infections, vaccinated people don't get as sick with Covid-19, studies show

Both studies show the vaccines strongly protect against severe disease and death, even months after people were first vaccinated and as the more transmissible Delta variant renewed the spread of the virus.

One large, ongoing study of 780,000 veterans shows all three vaccines being used in the US provide strong protection against death from Covid-19, even as their efficacy against mild and asymptomatic infection fell off dramatically.

Researchers looking at men and women getting treatment at Veterans Health Administration facilities found that overall vaccine efficacy against all types of infection fell from 87.9% in February to 48.1% in October. They only counted fully vaccinated veterans, and only counted test results from polymerase chain reaction (PCR) tests, the gold standard for determining infection.

"Although breakthrough infection increased risk of death, vaccination remained protective against death in persons who became infected during the Delta surge," the researchers wrote in their report, published in the journal Science.

"Our analysis by vaccine type, including the Pfizer-BioNTech, Moderna, and (Johnson & Johnson's) Janssen vaccines, suggests declining vaccine effectiveness against infection over time, particularly for the Janssen vaccine. Yet, despite increasing risk of infection due to the Delta variant, vaccine effectiveness against death remained high, and compared to unvaccinated Veterans, those fully vaccinated had a much lower risk of death after infection. These results demonstrate an urgent need to reinstate multiple layers of protection, such as masking and physical distancing -- even among vaccinated persons -- while also bolstering current efforts to increase vaccination."

The researchers say their data is more up to date than data provided by the US Centers for Disease Control and Prevention, although it looks only at veterans, who may not be representative of the US population. The group studied represents 2.7% of the US population and while it skews more heavily in favor of males, it may represent more minorities than other study groups, Barbara Cohn, an epidemiologist at the Oakland, California Public Health Institute who helped conduct the study, told CNN.

In March, Johnson & Johnson's vaccine was 86.4% effective in preventing any type of infection. By September, this had fallen to 13%, they reported.

In March, Moderna's vaccine was 89.2% effective in preventing any infection. This fell to 58% by September.

Pfizer's vaccine was 86.9% effective against any infection in March and effectiveness fell to 43.3% by September, they reported.

From July to October 2021, they found, vaccine effectiveness against death among veterans under 65 was 73% for J&J's Janssen vaccine, 81.5% for Moderna's, and 84.3% for Pfizer's and for those 65 and older it was 52.2% for Janssen's, 75.5% for Moderna's, and 70.1% for Pfizer's.

"Everybody does better if they are vaccinated, Janssen people included," Cohn said. "Vaccination is keeping people out of the hospital, even during Delta."

A second study was coordinated with the CDC and found that people vaccinated with either Pfizer's or Moderna's vaccines are much less likely to end up in the hospital on a ventilator or to die from infection than unvaccinated people.

Unvaccinated patients accounted for 91% of Covid-19 deaths and nearly 94% of those with a combined need for ventilators or death, the team reported in the Journal of the American Medical Association.

"We are very confident now that the vaccine is still helping you, even if you get Covid," Dr. Wesley Self, an associate professor at Vanderbilt University who led the study team, told CNN. "Even those who get sick don't get as sick as they would if they were unvaccinated."

The team at 21 US hospitals in 18 states studied 4,513 patients admitted to hospitals with respiratory diseases between March and July. "Unvaccinated patients accounted for 84.2% of COVID-19 hospitalizations. Hospitalization for COVID-19 was significantly associated with decreased likelihood of vaccination," the team wrote.

Not enough people had been vaccinated with Johnson & Johnson's Janssen vaccine to provide sufficient data for the study, Self said. He noted that other studies have shown the Janssen vaccine is less effective than the mRNA vaccines made by Pfizer and Moderna.

"We have known for several months that the mRNA vaccines prevent people from being infected with Covid and prevent people from being hospitalized with Covid. What was not clear from data before was if people still get Covid despite being vaccinated. Was the vaccine beneficial? The answer is a resounding yes," Self said.

"They are far less likely to become critically ill and die. That tells us the vaccines are attenuating the severity of disease."

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