NEW YORK CITY, New York: The Centers for Disease Control and Prevention relaxed its COVID-19 guidelines last week, driven by a recognition that an estimated 95 percent of Americans 16 and older have acquired some level of immunity, either from being vaccinated or earlier infected with Covid.

Americans will no longer need to quarantine themselves if they come in close contact with an infected person or stay at least 6 feet away from others, agency officials said.

"The current conditions of this pandemic are very different from those of the last two years," said the CDC's Greta Massetti, an author of the guidelines.

The CDC also dropped a "test-to-stay" recommendation, which said students exposed to COVID-19 could regularly test - instead of quarantining at home - to continue attending school. With no quarantine recommendation anymore, the testing option disappeared, too.

Masks continue to be recommended only in areas where community transmission is deemed high, or if a person is considered at high risk of severe illness.

The American Federation of Teachers, one of the nation's largest teachers unions, said it welcomes the guidance.

"Every educator and every parent starts every school year with great hope, and this year even more so," President Randi Weingarten said. "After two years of uncertainty and disruption, we need as normal a year as possible so we can focus like a laser on what kids need."

The new recommendations prioritize keeping children in school as much as possible, said Joseph Allen, director of Harvard University's healthy building program. Previous isolation policies forced millions of students to stay home from school, he said, even though the virus poses a relatively low risk to young people.

Others say the CDC is going too far in relaxing its guidelines.

Allowing students to return to school five days after infection, without proof of a negative COVID-19 test, could lead to outbreaks in schools, said Anne Sosin, a public health researcher at Dartmouth College. That could force entire schools to close temporarily if teachers get sick in large numbers, a dilemma that some schools faced last year.

"All of us want a stable school year, but wishful thinking is not the strategy for getting there," she said. "If we want a return to normal in our schools, we have to invest in the conditions for that, not just drop everything haphazardly like we're seeing across the country," she said, as reported by the Associated Press.

Also last week, the Food and Drug Administration updated its recommendations for how many times people exposed to COVID-19 should test, recommending three rapid antigen tests over two or three days, instead of two, to rule out infection.

FDA officials said the change was based on new studies that suggest the old protocol can miss too many infections and result in people spreading the coronavirus, especially if they do not develop symptoms.