Anthony Fauci

Vaccinations and residual immunity are among the reasons, President Biden's chief medical adviser, Anthony Fauci, said Tuesday, as the number of deaths drop and hospitalizations rise only slightly.

Anthony Fauci walks through what he predicts the BA.2 subvariant will do in the U.S., whether we will need boosters every four months and his advice for masking at indoor events.

Dr. Anthony Fauci, the nation's leading infectious disease expert, tells NPR's Morning Edition "it is so imminent to make sure that we get them boosted so that they would be in a protected zone."

"We are in a major surge now as we're going into the fall, into the school season. This is very serious business," Fauci said. He urges states and localities to mandate COVID-19 vaccines for teachers.

More contagious than other variants, and maybe more likely to cause severe disease, Delta is spreading so fast in the U.S. it could cause another surge this summer or fall, according to new research.

"If I had grandchildren, I would certainly recommend they get vaccinated," President Biden's chief medical adviser said. COVID-19 vaccines for younger children are being tested in clinical trials now.

Cases are up in some states, but the Biden administration's chief medical adviser says that "hopefully ... the vaccine is going to win this one." He urges continued mask-wearing and other measures.

"This is a national emergency. Four hundred thousand people have died. Everything is on the table across the whole supply chain," said Jeffrey Zients, the White House COVID-19 response coordinator.

The U.S. hit more than 4,000 deaths on Jan. 7, which also saw 274,703 new infections, according to Johns Hopkins University. The U.S. continues to lead the world in both cases and deaths.

More than 91,000 people were hospitalized with the coronavirus on Saturday — over 6,000 of them on ventilators. With the holiday season fast approaching, health experts fear the worst is yet to come.