A third COVID-19 vaccine is heading to clinics and pharmacies across the United States. But U.S. health officials are warning that another surge in cases could be on the horizon.Regulators authorized the vaccine from pharmaceutical company Johnson & Johnson over the weekend. Nearly 4 million doses are expected to be available at vaccination sites beginning as soon as Tuesday.But after a sharp fall over the past several weeks, the number of COVID-19 cases and deaths has increased again. Experts are concerned that newer, more infectious variants of the coronavirus that causes COVID-19 may be taking over.The reversal comes as most states are easing restrictions that contain the disease.”Now is not the time to relax the critical safeguards that we know can stop the spread of COVID-19,” Rochelle Walensky, director of the U.S. Centers for Disease Control and Prevention, said at a press briefing of the White House COVID-19 Response Team.Though the numbers have declined, the National Guard personnel check in people as they wait to receive a COVID-19 vaccination, Feb. 26, 2021, in Shelbyville, Tennessee.”Please hear me clearly,” Walensky said. “At this level of cases with variants spreading, we stand to completely lose the hard-earned ground we have gained. These variants are a very real threat to our people and our progress.”Effective against severe diseaseThe Johnson & Johnson vaccine was about 85% effective in preventing severe illness in a clinical trial spanning eight countries on three continents.That includes South Africa, where a more transmissible coronavirus variant dominates cases.”Even though the vaccine itself was not specifically directed against [that variant], it did extremely well when it came to preventing severe critical disease,” Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases and chief medical adviser to President Joe Biden, noted at the briefing.Though three vaccines are now available, experts are urging people not to try to pick and choose.”All three vaccines are safe and highly effective at preventing what we care about most, and that’s very serious illness and death,” Marcella Nunez-Smith, the Biden administration’s COVID-19 health equity task force chair, told reporters at the briefing.”As a physician, I strongly urge everyone in America to get the first vaccine that is available to you when it is your turn,” she said. “If people want to opt for one vaccine over another, they may have to wait. Time is of the essence. Getting vaccinated saves lives.”Easier to useUnlike the shots from Pfizer-BioNTech and Moderna, the Johnson & Johnson vaccine requires only one shot and does not need to be frozen.A pharmacist prepares a syringe with the Pfizer-BioNTech COVID-19 vaccine at a COVID-19 vaccination site at NYC Health + Hospitals Metropolitan, in New York, Feb. 18, 2021.This easier-to-use vaccine could be distributed in pop-up vaccination sites, mobile clinics or other places without freezers.Immediately after regulators gave the go-ahead, Johnson & Johnson began shipping its entire 3.9 million dose inventory of the vaccine. The company expects to deliver another 16 million doses by the end of March.But COVID-19 response coordinator Jeff Zients said supplies will be “uneven” for the next couple of weeks. He said most of the doses will arrive in late March.He urged people to continue wearing masks and social distancing, and to get vaccinated when their turn comes.”There is a path out of this pandemic,” he said, “but how quickly we exit this crisis depends on all of us.” 
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