WASHINGTON (CN) — One day after the number of Covid-19 cases reached a pandemic high in the United States, the director of the U.S. Centers for Disease Control and Prevention defended this week's announcement of shortened isolation and quarantine stints for people who have tested positive for or been exposed to the virus.
The CDC announced the changes on Monday: those who test positive are encouraged to isolate for five days, not 10 as previously recommended, if they are no longer symptomatic while continuing to wear a mask around family members and in public for five more days. For people who have been exposed to Covid-19, the center truncated the quarantine time to five days for unvaccinated people and those who haven't had their booster shot, while vaccinated and boosted individuals don't need to quarantine but should wear a mask in public or with family for 10 days.
CDC Director Rochelle Walensky defended the changes during a White House news conference Thursday, a day after the United States saw more than 265,000 new cases of Covid-19, the highest daily case count on record, as the highly contagious omicron variant continues to spread across the globe.
"These updates to our recommendations were made to reflect what we currently know about Covid-19 infection including how long a person is most infectious," Walensky said. "After five days, the risk of ongoing transmission substantially decreases. Let me make clear that we are standing on the shoulders of two years of science, two years of understanding transmissibility."
Walensky cited data showing that people are most infectious and likely to spread the virus during the two to three days before they show symptoms and for two to three days after. Between 85% and 90% of virus transmissions to other people happen in the first five days of someone being infected with Covid-19, she said.
Critics of the new guidelines have voiced frustration with the CDC not requiring a negative test for someone to end their isolation or quarantine periods, but Walensky said the data doesn't exist to back up a testing requirement.
“We know that PCR testing would not be helpful in this setting as people can remain PCR positive for up to 12 weeks after infection and long after they are transmissible and infectious,” Walensky said. "We also don't know that antigen tests give a good indication of transmissibility at this stage of infection."
The CDC director also said the data on infectious vaccinated and unvaccinated people do not show enough of a difference for the center to put out entirely different guidelines for each group.
Walensky emphasized the importance of masking, handwashing and testing before social gatherings as the most important measures to combat the spread of Covid-19.
“How well each of these prevention measures is implemented as well as adherence to isolation and quarantine recommendations will determine the outlook in the coming weeks and months," Walensky said.
The surge in Covid-19 cases has reinvigorated a push by the CDC and White House to encourage vaccinations and booster shots.
Nearly two-thirds of eligible seniors and 45% of eligible adults have received their booster shots, White House Covid-19 response coordinator Jeff Zients noted.
Anthony Fauci, the chief medical adviser to the president, pushed for Americans to get boosted. While the omicron variant has shown it can evade some levels of immunity developed from vaccinations and previous infections, Fauci said booster shots can increase people's protection from the virus.
"We know now, incontrovertibly, that this is a highly, highly transmissible virus," Fauci said.
With New Year's Eve fast approaching, Fauci gave the go-ahead for small home gatherings of boosted and vaccinated individuals to celebrate the new year, but cautioned against large gatherings.
"If your plans are to go to a 40-50-person New Year's Eve party with all the bells and whistles and everybody hugging and kissing and wishing each other a Happy New Year, I would strongly recommend that this year we do not do that,” Fauci said.
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