C.D.C. Study Raises Questions About Agency’s Isolation Guidelines

More than half of people who took a rapid antigen test five to nine days after they first tested positive for coronavirus or after developing symptoms of Covid-19 tested positive for the antigen. according to new research from the Centers for Disease Control and Prevention. The discovery raises more concerns about the agency’s revised isolation guidelines, which say many people with Covid can end periods of isolation after five days without a negative coronavirus test.

The CDC scientist who authored the study said he didn’t think the agency’s lockdown rules needed to be changed. But the results show that many people with the virus can still be contagious during this period, the scientists said.

The study “demonstrates what many suspected: five days is not enough for a significant number of people,” Angela Rasmussen, a virologist at the University of Saskatchewan Vaccine and Infectious Diseases Organization, wrote in an email. “The bottom line is,” she added, “that this should definitely lead to a change in isolation guidelines.”

The study came after Omicron became the dominant option in the United States and the number of cases skyrocketed across the country. Since then, the number of cases has plummeted, reducing the risk of infection and the number of Americans in isolation.

The CDC has reduced the lockdown period to five days from Dec 10 as the Omicron variant proliferates. Many public health experts have criticized the move, noting that people can still be contagious after five days and that allowing them to end isolation without testing could help the new variant spread faster.

Dr. Ian Plumb, a CDC medical epidemiologist and author of the new study, said he believes the study “mostly supports” the agency’s current lockdown guidance, which asks people to continue to take precautions, including wearing masks and not traveling. Until 10 full days have passed.

“Honestly, I don’t think that means the current leadership needs to be changed,” he said.

Instead, he says, the study supports the idea that antigen testing can be successfully integrated into isolation recommendations.

“I think the most important takeaway is that antigen tests can be included in isolation guidelines because they provide additional information about someone’s risk of being potentially contagious,” he said.

The new study was based on people who reported coronavirus infections to the Yukon-Kuskokwim Health Corporation, which provides health care to rural communities in southwest Alaska from Jan 1 to Feb 9.

In early January, the Yukon-Kuskokwim issued new lockdown rules. It recommends that people self-isolate for 10 full days after testing positive or showing symptoms of the virus. However, people who were asymptomatic or symptom-free and had been free of fever for at least 24 hours on days 5 through 9 of the isolation period were eligible for free Abbott BinaxNOW Rapid Antigen Testing administered by staff. Yukon-Kuskokwim If they test negative, they may end periods of isolation sooner.

Among 729 people who took antigen tests from days 5 to 9 of isolation, 54.3% tested positive. The proportion of people who tested positive declined over time, with 67.5% testing positive on day 5 of their isolation periods compared to 38.6% on day 9.

The researchers found that people with symptomatic infections were more likely to test positive by days 5-9 than those without symptoms. People who received a series of primary vaccines—two doses of the mRNA vaccine or one dose of the Johnson & Johnson vaccine—or were previously infected with the virus were less likely to test positive for the antigen during that time period than those who did not receive the vaccine or previously infected.

“Ultimately, I don’t think this is surprising given the data we’re seeing and the general concern of the infectious disease community about reducing isolation in the face of a new option,” said Saskia Popescu, an infectious disease epidemiologist at Georgetown Mason University. “But I do think it’s important that we continue to evaluate this, as antigen tests are not a perfect indicator of infectiousness and ability to transmit the virus.”

The findings are consistent with several other recent studies that have not yet been published in scientific journals or peer-reviewed by outside experts. In one, the researchers found that more than 40 percent of vaccinated health care workers gave a positive result of rapid tests for antigens on days 5-10 of illness.

IN two other studies, researchers found that a significant proportion of people with suspected and confirmed Omicron infection still had high viral loads more than five days after they first tested positive for the virus.

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