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It's time for coronavirus vaccine developers — and every American — to get serious about coronavirus variants.

As of Thursday, the more transmissible B1.351 COVID-19 variant first found in South Africa has been identified in the U.S., with other highly transmissible and potentially more deadly variants arriving earlier. That Thursday revelation should be "a wake up call to all of us," top coronavirus official Dr. Anthony Fauci said in a Friday briefing, making it clear that "will continue to see the evolution of mutants" as the pandemic continues.

Johnson & Johnson announced Friday that its one-shot coronavirus vaccine candidate is 66 percent effective at preventing the contraction of COVID-19, though it's less effective when faced with the B1.351 variant or the P1 first found in Brazil. Moderna's coronavirus vaccine is meanwhile just as effective against the B.1.1.7 variant first found in the U.K., but the company is still working on a booster shot to increase its effectiveness against the B1.351 strain.

Regardless of how effective these vaccines appear to be, Fauci said Friday that it's clear the coronavirus will continue to mutate to "evade pressure." He then called on vaccine developers to prepare to "adjust readily to make versions of a vaccine" that are "specifically" tailored to emerging variants. Dr. Rochelle Walensky echoed Fauci's suggestion, saying at the White House briefing that "we should be treating every case as it if it's a variant during this pandemic right now."

Fauci also said Friday that he hopes to have the U.S. start distributing vaccines to children by "late spring or early summer." The U.S. will soon launch small clinical trials to test the vaccines on children.