(NewsNation) — The Biden administration announced Wednesday that it is extending the nationwide mask requirement for public transit for 15 days as it monitors an uptick in COVID-19 cases.

The Centers for Disease Control and Prevention said it was extending the order, which was set to expire on Monday, until May 3 to allow more time to study the BA.2 omicron subvariant that is now responsible for the vast majority of cases in the U.S.

“In order to assess the potential impact the rise of cases has on severe disease, including hospitalizations and deaths, and health care system capacity, the CDC order will remain in place at this time,” the agency said in a statement.

When the Transportation Security Administration, which enforces the rule for planes, buses, trains and transit hubs, extended the requirement last month, it said the CDC had been hoping to roll out a more flexible masking strategy that would have replaced the nationwide requirement.

The mask mandate is the most visible vestige of government restrictions to control the pandemic, and possibly the most controversial. A surge of abusive and sometimes violent incidents on airplanes has been attributed mostly to disputes over mask-wearing.

Critics have seized on the fact that states have rolled back rules requiring masks in restaurants, stores and other indoor settings, and yet COVID-19 cases have fallen sharply since the omicron variant peaked in mid-January.

NewsNation Prime spoke Wednesday with infectious disease expert Dr. Monica Gandhi, a professor of medicine at the University of California San Francisco, who said, “we are actually in one of the best places in the pandemic that we have ever been.”

“It’s hard to tell sometimes from the news and from the extension of the federal mask mandate but in terms of hospitalizations, we are at our lowest point since spring of 2020 when we started to record them,” Gandhi said. “The rate of ICU admissions and deaths are falling even faster, falling by 28% a week.”

There has been a slight increase in cases in recent weeks, driven by the BA.2 strain, with daily confirmed cases nationwide rising from about 25,000 per day to more than 30,000. Those figures are an undercount since many people now test positive on at-home tests that are not reported to public health agencies.

Severe illnesses and deaths tend to lag infections by several weeks. The CDC is awaiting indications of whether the increase in cases correlates to a rise in adverse outcomes before announcing a less restrictive mask policy for travel.

Gandhi said the U.S. is in a “great place” right now for serious disease, likely because there is so much immunity among the population now.

She went on to say she did not agree with Philadelphia’s decision to return to an indoor mask mandate Monday.

Confirmed cased of COVID-19 rose more than 50% in 10 days in Philadelphia prior to the city announcing it would reinstate it’s mask mandate, according to the Associated Press.

Gandhi said she sees no benefit, but also sees no harm, at this time for anyone younger than 80 to receive a fourth dose of a COVID vaccine, after a study out of Israel suggested another dose of the vaccine would provide a limited defense against the omicron variant.

“The headline is it decreases mortality but if you look at the paper, there is very little benefit to a fourth shot,” Gandhi said. “In fact, what Europe did was say ‘fourth shot for anyone 80 and (older) but we don’t see any evidence for anyone younger than 80 at this point. No harm, but there is really no evidence for anyone younger than 80 to get it.'”

Children younger than 5, who are still ineligible to get the vaccine, should be able to receive it soon if the FDA acts quickly, Gandhi believes.

“It should just take the FDA a minute to approve this,” Gandhi said. “What Moderna put out was data of a 25 microgram dose from 6 months to 6 years old, given twice four weeks apart, and though it wasn’t very effective against mild disease, there were no hospitalizations, no severe disease. It’s ready, Moderna wants to give it and I think the FDA should approve the Moderna dose.”