CDC director says ‘what we thought people would tolerate’ was factor in quarantine decision

WASHINGTON, DC -- Sweeping new Covid-19 isolation and quarantine guidelines were spurred by scientific research and what Americans would likely tolerate, the director of the U.S. Centers for Disease Control and Prevention said Wednesday.

They come as doctors expect the holiday coronavirus surge, driven by the highly contagious Omicron variant, to get worse following New Year's Eve. The average number of daily US Covid-19 cases on Tuesday reached 265,427 -- a new pandemic high, according to data from Johns Hopkins University.

In guidance issued this week, the CDC said:

• Anyone who tests positive for Covid-19, regardless of vaccination status, can stop isolating after five days if they don't have symptoms or if their "symptoms are resolving" -- as long as they also wear a mask around others for the next five days. (Previously, the CDC recommended anyone with Covid-19 isolate for 10 days.)

• Recently fully vaccinated or boosted people who were exposed to someone with Covid-19 don't need to quarantine, as long as they don't get symptoms. (But they should wear a mask around others for 10 days and try to get tested five days after exposure.)

• Unvaccinated people and those who got shots some time ago and were exposed to someone with Covid-19 need to quarantine for five days after exposure. This covers people who got their last dose of the Pfizer or Moderna vaccine more than six months ago and haven't been boosted; or got just one shot of the Johnson & Johnson vaccine more than two months ago and haven't been boosted. (Everyone in this category, too, should try to get tested five days after exposure and wear a mask around others for the next five days.)

Many have asked why the CDC reduced isolation times for some people with Covid-19 -- but didn't recommend taking a test to confirm whether they were still infected. PCR and antigen tests aren't always good indicators of whether someone is still contagious, CDC Director Dr. Rochelle Walensky told CNN on Wednesday.

"What we do know is that the PCR test after infection can be positive for up to 12 weeks, so that is not going to be helpful. You're not going to be transmitting during all of that period of time," Walensky said.

"So then the question is, well why not do an antigen test at five days? We do know some people at five days will be negative and still be able to transmit. We also know that some people will be positive and still be able to transmit," she said.

"So that antigen test was actually not authorized for this purpose, and its information will not be useful. Regardless of what the antigen test said, we would say you still need to wear your mask for five days."

Why shorten isolation times?

New research, combined with some people's reluctance to isolate for 10 days if infected, spurred some of the latest guidance, Walensky said.

"We know that the most amount of transmission occurs in those one to two days before you develop symptoms (to) those two to three days after you develop symptoms," she said.

"And if you map that out, those five days account for somewhere between 85% to 90% of all transmission that occurs."

So for those who test positive but have no symptoms or dwindling symptoms at Day 5, "we shortened the time to encourage people to do the right thing," Walensky said.

"We don't want them out and about when they are maximally infectious."

Why must health care workers test out of isolation but not others?

As some hospitals get overwhelmed during the Omicron variant surge, the CDC issued emergency guidance for health care workers last week saying:

• Those with Covid-19 who are asymptomatic can return to work after seven days with a negative test. And that isolation time can be cut further if there are staffing shortages.

• Health care workers who have received all recommended Covid-19 vaccine doses, including a booster, do not need to quarantine at home following high-risk exposures.

Asked why infected health care workers should get tested before going back to work -- but other infected Americans don't have to -- Walensky said infection control recommendations in health care settings are "always more stringent" than for the general public.

The decision had nothing to do with shortages of rapid antigen tests, she said.

"We wouldn't change our guidance based on the result of that rapid test," Walensky said. "And you know that it didn't have anything to do with any shortage at all because we recommend rapid tests for those in quarantine."

But CNN medical analyst Dr. Jonathan Reiner said the CDC's explanation is confusing.

While PCR tests can sometimes "detect the virus when a person is no longer infectious," antigen tests are more likely to turn up positive only when a person is actively contagious, Reiner told CNN on Wednesday.

"What I don't understand is why a test which has a very, very low false positivity rate ... why this would not be a useful tool not to for telling people at Day 5 when they can go back to work," Reiner said.

New Covid-19 record set as schools plan to reopen

The nationwide coronavirus case spike comes just as millions of children are getting ready to go back to school next week and as pediatric Covid-19 hospitalizations have risen.

Pediatrician Dr. Peter Hotez said he thinks some schools in areas of very high transmission should delay a return to in-person learning.

"I wouldn't do it now," Hotez said Tuesday night. "You have got a screaming level of transmission in the Northeast, in New York City and Washington, DC. Trying to open schools at this point, it's hard to imagine how things will go well."

But the US Department of Education is urging school districts to take safety measures to ensure classrooms remain open for in-person learning in the second half of the school year, according to a new resource guide addressed to school leaders and obtained Monday by CNN.

"It is incredibly important that all schools work to remain open for in-person learning five days a week, especially in light of the Omicron variant," the guide said.

Despite a recent onslaught of Covid-19 cases in New York City, the nation's largest public school system will reopen as planned next Monday, Mayor Bill de Blasio said. The city's public schools will give a week's worth of at-home tests to students who test positive so they can monitor their condition and return as soon as it's safe, he said Tuesday.

Child hospitalizations creep toward pandemic peak

Across the country, an average of 305 children were fighting Covid-19 in a hospital on any given day during the week that ended Sunday, according to data from the Centers for Disease Control and Prevention and the US Department of Health and Human Services.

That's a more than 48% increase from the previous week and 10.7% lower than the peak average of 342 children who were admitted to hospitals with the virus at the end of August and early September.

While everyone age 5 and older in the US is eligible to get a vaccine, about 40% of the total population is not fully vaccinated, putting them at a higher risk for Covid-19's most severe outcomes, including serious illness and death.

The number of children who need medical attention at Children's National Hospital in Washington, DC, has nearly doubled, said Dr. Roberta DeBiasi, division chief of infectious diseases at the hospital.

The hospital admitted about 20 children at its peak, but that number has jumped to between 40 and 50 during the Omicron surge, DeBiasi said. Most of the patients are unvaccinated, partially vaccinated or immunocompromised, she said.

"So that is really the big difference, and it's not because the virus is more severe. It's because the overall infectivity and number of cases has really shot up," DeBiasi said.

Even so, hospital staff have been able to keep the mortality rate low, she said. "Even our children that are extremely ill, critically ill, we've gotten very good at taking care of these children."

In New York City, pediatric hospitalizations increased five-fold over a three-week period.

And at the Lurie Children's Hospital of Chicago, Covid-19 cases are roughly three times higher than the hospital's previous peak in December 2020. In the past week, hospitalizations are four times higher what the hospital typically sees.

Overall, experts are warning the next few weeks will be rough for the country.

"There's no question that January will be filled with a lot of short-term challenges -- hospital beds, staffing shortages, tests, shortages of almost everything," said Andy Slavitt, former senior adviser to the Biden administration's Covid-19 response team.

"It's tough for the system to handle this many cases at once."

Antigen tests are less sensitive to Omicron, FDA says

Health experts say at-home antigen tests that turn out to be positive are a good sign a person is truly infected. However, rapid tests might not pick up the new Omicron variant as well as previous strains, the US Food and Drug Administration said Tuesday.

Studies on antigen tests that used patient samples that had the live virus showed that while the tests detect the Omicron variant, they did so with less sensitivity, the FDA said.

Sensitivity measures how often a test can give a positive result when someone has the disease.

More studies on the tests are ongoing, and people should continue using them, the FDA said.

"The tests are still worthwhile. Don't let anybody think that the FDA was saying that tests are no longer good," said Dr. Anthony Fauci, director National Institute of Allergy and Infectious Diseases. "They say they're less sensitive now. They never were 100% sensitive."