Americans should get vaccinated as quickly as possible when their turn comes, and shouldn’t wait for the next generation of vaccines in hopes for more protection against variants, said Dr. Anthony Fauci, the nation’s leading infectious disease expert.

"You need to get vaccinated when it becomes available, as quickly and as expeditiously as possible throughout the country," Fauci said during a White House COVID-19 Response Team briefing on Monday. "The reason for that is that there is a fact that permeates virology, and that is, that viruses cannot mutate if they don’t replicate."

Widespread vaccination prevents the SARS-CoV-2 virus from having an "open playing field," Fauci said. Prompt vaccinations can protect people against disease, infection and prevent emerging strains in the U.S. and overseas. 

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Early data suggests vaccines will remain effective against variants, though one strain, in particular, first detected in South Africa, has diminished vaccines’ efficacy.

Moderna, for instance, announced last week that trial results showed no significant impact in the vaccine’s effectiveness of neutralizing the virus, despite the introduction of new variants, according to a news release. However, the company will forge ahead with plans to test a booster shot "to further increase neutralizing titers against emerging strains," as well as advance another variant booster candidate specifically against the South African variant.

Pfizer and BioNTech already voiced confidence in their COVID-19 vaccine's ability to protect against new variants and previously touted flexibility in the mRNA vaccine platform to tweak vaccines if necessary.

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Meanwhile, new results on a vaccine developed by Johnson & Johnson revealed the jab was 72% effective in preventing moderate-to-severe COVID-19 in the U.S. but fell to 66% in a larger trial conducted worldwide. 

J&J boosted hopes its vaccine candidate will be effective against variant strains, and the company plans to file for an emergency use authorization (EUA) in the U.S. in early February, with the product ready to ship immediately after authorization. 

Another vaccine in the pipeline, developed by Novavax, highlighted the South African strain’s ability to diminish vaccine efficacy. Recent findings from Novavax reveal its vaccine is 89% effective against COVID-19 illness but plummeted to 60% among trial volunteers in South Africa. Overall the protection against the South African variant was 49%, the company said. 

Dr. Rochelle Walensky, the new director of the Centers for Disease Control and Prevention (CDC), said people can take several steps to protect against variants amid high case counts and emerging strains.

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"First, wear a mask, stay six feet apart when you are in public and around others who do not live in your household," Walensky said during the briefing. "Second, please avoid crowds and poorly ventilated areas. Third, now is not the time to travel, but if you must travel, you must wear a mask and follow other CDC and local guidance in order to protect yourself and others while you travel. And finally, please get vaccinated when it’s your turn."

The guidance from health officials has not shifted amid emerging variants, but officials have urged the public to double down on these mitigation steps to protect against the novel virus and its emerging strains.

Fox News' Alexandria Hein contributed to this article.