According to a new study by the Centers for Disease Control and Prevention, more than half of those who took a rapid test for antigen five to nine days after their first test for coronavirus or after developing Covid-19 symptoms were positive.
The finding raises more concerns about the agency’s revised isolation guidelines, which say that many people with Covid can end their isolation periods after five days, without a negative coronavirus test.
C.D.C. scientist who was an author of the study said that he did not believe the agency’s isolation guidelines needed to change. Scientists said that the results indicate that the virus could still be transmitted to many people during this time.
The study “demonstrates what a lot of people have suspected: that five days is insufficient for a substantial number of people,” Angela Rasmussen, a virologist at the Vaccine and Infectious Disease Organization at the University of Saskatchewan, said in an email. “The bottom line,” she added, “is that this absolutely should lead to a change in isolation guidance.”
The research was initiated after Omicron was declared the dominant variant in the United States. Also, cases were on the rise across the country. The incidence of infections has declined precipitously and isolation rates have decreased.
The C.D.C. The C.D.C. reduced the isolation period from 10 days in December to five days because of the Omicron variant spreading. Many public health experts criticised the move, pointing out that people could still be infected after five working days, and that allowing them the option to end isolation without being tested might speed up the spread of the new variant.
Dr. Ian Plumb, a C.D.C. medical epidemiologist, said that he believes the study “basically supported” the agency’s current isolation guidance. and an author of the new study, said that he believed the study “basically supported” the agency’s current isolation guidance, which asks people to continue taking precautions — including wearing masks and refraining from travel — until 10 full days have passed.
“I honestly don’t think that it means that the current guidance needs to” change, he said.
He stated that the study supports his belief that antigen testing can be successfully integrated into isolation protocols.
“I think the biggest takeaway is that it’s possible to incorporate antigen tests into the guidance for isolation because they provide additional information about someone’s risk of being potentially infectious,” he said.
The new study was based upon people who had coronavirus infections reported to Yukon-Kuskokwim Health Corporation (which provides health care for rural communities in southwestern Alaska) between Jan. 1 and Feb. 9.
Yukon-Kuskokwim published new isolation guidelines in January. It recommends that people be isolated for a minimum of 10 days after they develop symptoms or test positive for the virus. Yukon-Kuskokwim staff administered the rapid antigen test Abbott BinaxNOW to people who did not experience any symptoms or resolved their symptoms within the last 10 days. They could be isolated if they test negative.
54.3 percent of the 729 people who tested positive for antigens on Days 5-9 of their isolation periods were positive. The percentage of people who tested positive has declined over time. 67.5 percent tested positive on Day 5, compared to 38.6 percent on Days 9 and 10.
The researchers found that people who had symptomatic infection were more likely to test positive for the virus on Days 5-9 than those who were asymptomatic. People who had received a primary vaccine series — two doses of an mRNA vaccine or a single dose of Johnson & Johnson’s shot — or had been previously infected by the virus were less likely to receive positive antigen results during this time frame than those who had not been vaccinated or previously infected.
“Ultimately, I don’t think this is surprising based off the data we’re seeing and the general concern from the infectious disease community on shortening isolation in the face of a novel variant,” said Saskia Popescu, an infectious disease epidemiologist at George Mason University. “But I do think it’s important we continue to assess this, as antigen tests aren’t a perfect proxy for infectiousness and ability to transmit the virus.”
These findings are consistent in several other studies that have been done recently but not yet published in scientific journals or reviewed outside experts. Researchers found that over 40% of vaccinated health workers were positive for rapid antigen tests on days 5-10 of their illnesses.
Two other studies showed that Omicron infection patients with suspected or confirmed Omicron were still at high levels of viral load five days after being tested positive.
Source: NY Times
