If approved, a rollout of the J&J vaccine could add enough shots by the end of March to boost the total number of people vaccinated by 20%.

More than 2,100 cases linked to variants first identified in the U.K., South Africa and Brazil have now been detected in the U.S., according to the CDC.

Johnson & Johnson’s single-dose Covid-19 vaccine worked safely and should be authorized for use in the U.S., a panel of experts advised federal health regulators Friday.

The vaccine’s effectiveness and safety results were “way over the bar,” said Eric Rubin, a panel member who is editor-in-chief of the New England Journal of Medicine.

During the all-day public meeting, representatives from the FDA and J&J discussed the safety and effectiveness of the company’s vaccine in a 44,000-plus subject study, as well as how effective the J&J vaccine is in preventing new cases caused by variants.

The vaccine was 66% effective at protecting people from moderate to severe Covid-19, an FDA review found, and even more effective at preventing severe disease alone.

“The increased volume of sequence information is helping us to better understand the diversity of variants circulating in the United States, where they are located, and how they are spread,” she said Wednesday at a White House Covid-19 Response Team press briefing.

The increase in sequencing comes as new coronavirus variants are spreading in various parts of the U.S.

“Most mutations that occur do not cause the virus to be more infectious or deadly, but some variants have mutations that are more concerning,” said Ajay Sethi, an associate professor at the University of Wisconsin–Madison.

Public-health officials have said the variant first identified in the U.K.

The South Africa variant appears to make some Covid-19 vaccines less effective and has raised concerns that people who already had the disease could get it again from the new strain.

A study by Pfizer found that its vaccine works against the variants identified in South Africa and the U.K.

variant has been found in 1,881 cases in 45 states as of Thursday, according to the CDC.

The South Africa variant has been found in 46 cases in 14 states, and the Covid-19 mutation from Brazil has been in five cases in four states.

“For the new variants, I think it’s a bit premature to really declare what we’re seeing and this reinforces that we need more genomic sequencing and to be vigilant in our infection prevention and public health control measures while we learn more about them,” said Saskia Popescu, an assistant professor in the Biodefense Program at the Schar School of Policy and Government at George Mason University.

“More infectiousness will result in more cases, more hospitalizations, and more deaths in unvaccinated people,” he said.

The vaccination effort at long-term care facilities was launched in a few states in mid-December, ramped up from there and by Thursday more than 4.5 million people linked to these senior sites received at least one dose, according to the Centers for Disease Control and Prevention.

The American Health Care Association, a long-term care industry group, estimates there are roughly 4.4 million residents and staffers at nursing homes and assisted-living facilities, two prominent kinds of long-term care facilities.

More than 2.2 million people associated with long-term care have gotten their second dose, according to the CDC.

The vaccination effort in the society as a whole has yet to reach so deeply, with about 47.2 million people having received one or more doses, or 14.2% of the population, according to the CDC

Epidemiologists have said it is difficult to tell if vaccinations are having a broader impact yet, even as cases and hospitalizations have fallen from the wintertime peak