The CDC's advisory committee recommended Thursday that people who have a choice should get an mRNA vaccine, either Pfizer or Moderna, over the single-shot Johnson & Johnson vaccine after a review of new CDC data on rare blood clots linked to J&J.

The vote was unanimous.

The rare blood clots are not a new safety concern and the vaccine has already become far less common in the U.S. after it was given an FDA warning label about the clotting condition. But more data that confirmed a slightly higher rate of clotting cases and deaths than was previously reported caused the CDC and FDA to take another look at the data this week.

The CDC has confirmed nine deaths and 54 cases from the severe clotting event, thrombosis with thrombocytopenia.

There could also be more cases and deaths because TSS is under-diagnosed and could be underreported, the CDC said.

The clotting is more common among women in their 30s and 40s but has been seen in adult men and women of all ages.

The experts said J&J should not be taken off the shelves and is still far more beneficial than not getting any vaccine at all.

-ABC News' Cheyenne Haslett

Maine and New Hampshire are now averaging more new cases than at any other point in the pandemic, while daily cases in Massachusetts, Vermont, Connecticut, Pennsylvania and Rhode Island are nearing peak levels, according to federal data.

Five of those states -- Connecticut, Maine, Massachusetts, Rhode Island and Vermont -- have the highest full vaccination rates in the country.

In Florida, which has been largely spared from the latest COVID-19 wave, daily cases have increased by 92% over the last two weeks, according to federal data.

-ABC News' Arielle Mitropoulos

COVID-19 cases in New York City have tripled in the last month, officials warned Thursday.

Mayor Bill de Blasio announced a six-point plan to fight the surge, including increasing testing capacity, doubling down on business inspections and distributing 1 million KN95 masks and 500,000 rapid home tests.

"We need to stop this variant," the mayor said. "This variant moves fast. We need to move a lot faster."

-ABC News' Aaron Katersky

Dr. Anthony Fauci, the nation's leading expert on infectious diseases, warned Thursday that omicron will become the dominant variant of the novel coronavirus in the United States "very soon."

"It has an extraordinary ability to transmit efficiently and spread," Fauci, the chief medical advisor to U.S. President Joe Biden, told ABC News' George Stephanopoulos in an interview on "Good Morning America."

"It has what we call a doubling time of about three days and if you do the math on that, if you have just a couple of percentage of the isolates being omicron, very soon it's going to be the dominant variant," he explained. "We've seen that in South Africa, we're seeing it in the U.K. and I'm absolutely certain that's what we're going to be seeing here relatively soon."

Fauci, who is also the director of the National Institute of Allergy and Infectious Diseases, urged Americans to "absolutely" get vaccinated against COVID-19, if they haven't already, and to also receive a booster shot when they become eligible.

"At this point, we don't believe you need an omicron-specific boost," he added. "We just need to get the boost with what you got originally for the primary vaccination."

"Omicron is spreading at a rate we have not seen with any previous variant," World Health Organization Director-General Dr. Tedros Adhanom Ghebreyesus warned Tuesday.

Omicron has been reported in 77 countries, he said, adding that the new variant is likely in most countries.

Tedros said health officials are "concerned that people are dismissing omicron as mild."

"Even if omicron does cause less severe disease, the sheer number of cases could once again overwhelm unprepared health systems," he said.

-ABC News' Christine Theodorou