WASHINGTON (NewsNation Now) — A team of scientists and public health experts assembled by President Joe Biden briefed the public on the nation’s COVID-19 response efforts Friday, just one day after a new variant was identified in the U.S.

Dr. Anthony Fauci said the emergence and increasing spread of coronavirus mutations means that vaccine makers must be ready to make new shots to stay ahead of the public health crisis.

“You can be almost certain that as long as there is a lot of virus circulating in the community, there will be the evolution of mutants, because that is what viruses do,” the government’s top infectious disease expert said Friday.

“This is a wake-up call to all of us,” says Fauci, noting government scientists will be working to keep pace with virus mutations.

The nature of viruses is to change in ways that promote their spread, Fauci says. The evolution of mutant versions means scientists need to be “nimble” and ready to make tweaks to vaccines. So far, the mutants haven’t overwhelmed the protective power of vaccines.

Moderna said Monday that its vaccine is effective against emerging variants of coronavirus that have appeared in the United Kingdom and South Africa. But it said it would test a vaccine booster and an altered booster against the South African variant in pre-clinical trials to see if that would be more effective in boosting antibodies against the variant and other future variants. 

Fauci also said the latest results of the Johnson & Johnson vaccine trial were “encouraging”.

J&J said Friday that in the U.S. and seven other countries, the single-shot vaccine was 66% effective overall at preventing moderate to severe illness, and much more protective — 85% — against the most serious symptoms.

Fauci urged people to look beyond the vaccine to vaccine efficacy results, noting “is a single shot vaccine in which you start to see efficacy anywhere from seven to 10 days.”

Senior advisor Andy Slavitt said seven states had provided the first vaccine dose to more than 10% of their adult populations. The states Slavitt listed were: Alaska, West Virginia, New Mexico, Connecticut, North Dakota, Oklahoma and South Dakota.

The White House COVID-19 Response Team held a briefing earlier this week, when the variant first identified in South Africa hadn’t yet been detected in the country.

State health officials in South Carolina confirmed two cases of the strain on Thursday. Public health officials said it’s almost certain that there are more infections that have not been identified yet. They’ve also expressed concern that this version spreads more easily and that vaccines could be less effective against it.

The two cases were discovered in adults in different regions of the state and do not appear to be connected. Neither of the people infected has traveled recently, the South Carolina Department of Health and Environmental Control said Thursday.

South Africa first detected the variant in October. Since then, it’s been found in at least 30 other countries.

Viruses are constantly mutating, with coronavirus variants circulating around the globe, but scientists are primarily concerned with the emergence of three of them. Other variants first reported in the United Kingdom and Brazil were previously confirmed in the U.S.

Some tests suggest the South African and Brazilian variants may be less susceptible to antibody drugs or antibody-rich blood from COVID-19 survivors, both of which help people fight off the virus.

The Associated Press contributed to this report.