U.S. regulators said Friday they are no longer considering authorizing a second COVID-19 booster shot for all adults under 50 this summer, focusing instead on revamped vaccines for the fall that will target the newest viral subvariants. Pfizer and Moderna expect to have updated versions of their shots available as early as September, the Food and Drug Administration said in a statement. That would set the stage for a fall booster campaign to strengthen protection against the latest versions of omicron. The announcement means the U.S. won’t pursue a summer round of boosters using the current vaccines for adults under 50, as some Biden administration officials and outside experts previously suggested. They had argued that another round of shots now could help head off rising cases and hospitalizations caused by the highly transmissible omicron strains. Currently, all Americans age 5 and over are eligible for a booster shot five months after their initial primary series. Fourth doses of the Pfizer or Moderna shots — a second booster — are recommended for Americans 50 and older and for younger people with serious health issues that make them more vulnerable to COVID-19. The FDA urged eligible adults who haven’t been boosted to get their extra shot now: “You can still benefit from existing booster options and leave time to receive an updated booster in the fall,” the agency said in a statement. The White House has also emphasized that getting a fourth dose now won’t impact anyone’s ability to get omicron-targeted shots once they’re made available — although how long its been since their last dose will play a role in how soon they’re eligible. Two omicron subvariants, BA.4 and BA.5, are even more contagious than their predecessors and have pushed new daily cases above 125,000 and hospitalizations to 6,300. Those are the highest levels since February, though deaths have remained low at about 360 per day, thanks to widespread immunity and improved treatments against the virus. The subvariants are offshoots of the strain responsible for nearly all of the virus spread in the U.S. this year. All the COVID-19 vaccines given in the U.S. until now have been based on the original version of the virus that began spreading across the country in early 2020. In June, the FDA told the vaccine makers that any boosters for the fall would have to combine protection against omicron BA.4 and BA.5 and the original coronavirus strain. Both manufacturers have been speeding their production and data gathering to have those so-called bivalent vaccines ready for the fall. The FDA and the Centers for Disease Control and Prevention would have to sign off on revamped shots before their launch. Also read: Global Covid cases top 578 million The U.S. has a contract to buy 105 million doses of the Pfizer combination shots once they’re ready, and 66 million of Moderna’s version. But how soon large amounts would become available isn’t clear. The government contracts include options to purchase 300 million doses each, but reaching that total will require more funding from Congress, the Biden administration said. As for timing, getting a booster too soon after the previous dose means missing out on its full benefit — something policymakers will have to take into consideration when rolling out revamped shots. The White House has at times been frustrated by the pace of decision-making at the FDA and CDC, most notably last summer, when the regulators took weeks to decide whether to authorize the first booster dose for U.S. adults. Privately, West Wing officials believe the delay cost lives, preventing optimum protection amid the delta and omicron surges, but also fed into doubts about vaccine and booster effectiveness that impacted their uptake. In recent weeks, some of those frustrations have bubbled up again, as regulators considered whether to recommend a fourth shot for all adults, not just those at highest risk from the virus. Some in the White House believe that the additional dose would have helped somewhat with the rapidly spreading BA.5 subvariant, and also lift the confidence of anyone worried that their protection had waned.    Still, officials across the government have acknowledged the risks of vaccine fatigue among Americans, including tens of millions who still haven’t received their first booster. Government figures show less than half of those eligible for a booster have gotten that third shot.

The U.S. is urging that everyone 12 and older get a COVID-19 booster as soon as they’re eligible, to help fight back the hugely contagious omicron mutant that’s ripping through the country. Boosters already were encouraged for all Americans 16 and older, but Wednesday the Centers for Disease Control and Prevention endorsed an extra Pfizer shot for younger teens — those 12 to 15 — and strengthened its recommendation that 16- and 17-year-olds get it, too. “It is critical that we protect our children and teens from COVID-19 infection and the complications of severe disease,” Dr. Rochelle Walensky, the CDC’s director, said in a statement Wednesday night. “This booster dose will provide optimized protection against COVID-19 and the Omicron variant. I encourage all parents to keep their children up to date with CDC’s COVID-19 vaccine recommendations,” she said. Also read: FDA paves way for Pfizer COVID-19 vaccinations in young kids Vaccines still offer strong protection against serious illness from any type of COVID-19, including omicron — what experts say is their most important benefit. But the newest mutant can slip past a layer of the vaccines’ protection to cause milder infections. Studies show a booster dose at least temporarily revs up virus-fighting antibodies to levels that offer the best chance at avoiding symptomatic infection, even from omicron. Earlier Wednesday, the CDC’s independent scientific advisers wrestled with whether a booster should be an option for younger teens, who tend not to get as sick from COVID-19 as adults, or more strongly recommended. Giving teens a booster for a temporary jump in protection against infections is like playing whack-a-mole, cautioned CDC adviser Dr. Sarah Long of Drexel University. But she said the extra shot was worth it to help push back the omicron mutant and shield kids from the missed school and other problems that come with even a very mild case of COVID-19. Also read: Pfizer asks FDA to OK COVID-19 booster shots for all adults More important, if a child with a mild infection spreads it to a more vulnerable parent or grandparent who then dies, the impact “is absolutely crushing,” said panelist Dr. Camille Kotton of Massachusetts General Hospital. “Let’s whack this one down,” agreed Dr. Jamie Loehr of Cayuga Family Medicine in Ithaca, New York. The vaccine made by Pfizer and its partner BioNTech is the only option for American children of any age. The CDC says about 13.5 million children ages 12 to 17 — slightly more than half of that age group — have received two Pfizer shots. Boosters were opened to the 16- and 17-year-olds last month. Wednesday’s decision means about 5 million of the younger teens who had their last shot in the spring are eligible for a booster right away. New U.S. guidelines say anyone who received two Pfizer vaccinations and is eligible for a booster can get it five months after their last shot, rather than the six months previously recommended. But one committee member, Dr. Helen Keipp Talbot of Vanderbilt University, worried that such a strong recommendation for teen boosters would distract from getting shots into the arms of kids who have not been vaccinated at all. The advisers saw U.S. data making clear that symptomatic COVID-19 cases and hospitalizations are between seven and 11 times higher in unvaccinated adolescents than vaccinated ones. While children do tend to suffer less serious illness from COVID-19 than adults, child hospitalizations are rising during the omicron wave -- the vast majority of them unvaccinated. During the public comment part of Wednesday’s meeting, Dr. Julie Boom of Texas Children’s Hospital said a booster recommendation for younger teens “cannot come soon enough.” The chief safety question for adolescents is a rare side effect called myocarditis, a type of heart inflammation seen mostly in younger men and teen boys who get either the Pfizer or Moderna vaccines. The vast majority of cases are mild — far milder than the heart inflammation COVID-19 can cause — and they seem to peak in older teens, those 16 and 17. The FDA decided a booster dose was as safe for the younger teens as the older ones based largely on data from 6,300 12- to 15-year-olds in Israel who got a Pfizer booster five months after their second dose. Israeli officials said Wednesday that they’ve seen two cases of mild myocarditis in this age group after giving more boosters, 40,000. Earlier this week, FDA vaccine chief Dr. Peter Marks said the side effect occurs in about 1 in 10,000 men and boys ages 16 to 30 after their second shot. But he said a third dose appears less risky, by about a third, probably because more time has passed before the booster than between the first two shots.

U.S. health authorities again expanded the nation's booster campaign Thursday, opening extra doses of Pfizer’s COVID-19 vaccine to several million 16- and 17-year-olds. The U.S. and many other nations already were urging adults to get booster shots to pump up immunity that can wane months after vaccination, calls that intensified with the discovery of the worrisome new omicron variant. On Thursday, the Food and Drug Administration gave emergency authorization for 16- and 17-year-olds to get a third dose of the vaccine made by Pfizer and its partner BioNTech — once they're six months past their last dose. And hours later, the Centers for Disease Control and Prevention lifted the last barrier as Dr. Rochelle Walensky, the agency's director, issued a statement strongly encouraging those teens to get their booster as soon as it's time. Boosters are important considering that protection against infection wanes over time and “we’re facing a variant that has the potential to require more immunity to be protected," Walensky told The Associated Press. Also read: Pfizer says COVID booster offers protection against omicron About 200 million Americans are fully vaccinated, including about 4.7 million 16- and 17-year-olds, many of whom got their first shots in the spring and would be eligible for a booster. “Vaccination and getting a booster when eligible, along with other preventive measures like masking and avoiding large crowds and poorly ventilated spaces, remain our most effective methods for fighting COVID-19,” Dr. Janet Woodcock, acting FDA commissioner, said in a statement. The Pfizer vaccine is the only option in the U.S. for anyone younger than 18, either for initial vaccination or for use as a booster. It’s not yet clear if or when teens younger than 16 might need a third Pfizer dose. But Walensky said the CDC and FDA would closely watch data on 12- to 15-year-olds because if they eventually need boosters, “we again will want to act swiftly.” Vaccinations for children as young as 5 just began last month, using special low-dose Pfizer shots. By this week, about 5 million 5- to 11-year-olds had gotten a first dose. The extra-contagious delta variant is causing nearly all COVID-19 infections in the U.S., and in much of the world. It’s not yet clear how vaccines will hold up against the new and markedly different omicron mutant. But there’s strong evidence that boosters offer a jump in protection against delta-caused infections, currently the biggest threat. “The booster vaccination increases the level of immunity and dramatically improves protection against COVID-19 in all age groups studied so far,” BioNTech CEO Ugur Sahin said in a statement. Complicating the decision to extend boosters to 16- and 17-year-olds is that the Pfizer shot — and a similar vaccine made by Moderna — have been linked to a rare side effect. Called myocarditis, it’s a type of heart inflammation seen mostly in younger men and teen boys. Also read: Vaccine makers racing to update COVID shots, just in case The FDA said rising COVID-19 cases in the U.S. mean the benefits of boosters greatly outweighed the potential risk from the rare side effect, especially as the coronavirus itself can cause more serious heart inflammation. Health officials in Israel, which already gives boosters to teens, have said the side effect continues to be rare with third doses. A U.S. study this week offered additional reassurance. Researchers from children’s hospitals around the country checked medical records and found the rare side effect usually is mild and people recover quickly. The research was published Monday in the journal Circulation.