The Centers for Disease Control and Prevention on Thursday endorsed booster shots for millions of older or otherwise vulnerable Americans, opening a major new phase in the U.S vaccination drive against COVID-19. CDC Director Dr. Rochelle Walensky signed off on a series of recommendations from a panel of advisers late Thursday. The advisers said boosters should be offered to people 65 and older, nursing home residents and those ages 50 to 64 who have risky underlying health problems. The extra dose would be given once they are at least six months past their last Pfizer shot. However, Walensky decided to make one recommendation that the panel had rejected. The panel on Thursday voted against saying that people can get a booster if they are ages 18 to 64 years and are health-care workers or have another job that puts them at increased risk of being exposed to the virus. But Walensky disagreed and put that recommendation back in, noting that such a move aligns with an FDA booster authorization decision earlier this week. The category she included covers people who live in institutional settings that increase their risk of exposure, such as prisons or homeless shelters, as well as health care workers. Read:CDC panel grapples with who needs a COVID-19 booster shot The panel had offered the option of a booster for those ages 18 to 49 who have chronic health problems and want one. But the advisers refused to go further and open boosters to otherwise healthy front-line health care workers who aren't at risk of severe illness but want to avoid even a mild infection. The panel voted 9 to 6 to reject that proposal. But Walensky decided to disregard the advisory committee's counsel on that issue. In a decision several hours after the panel adjourned, Walensky issued a statement saying she had restored the recommendation. “As CDC Director, it is my job to recognize where our actions can have the greatest impact,” Walensky said in a statement late Thursday night. “At CDC, we are tasked with analyzing complex, often imperfect data to make concrete recommendations that optimize health. In a pandemic, even with uncertainty, we must take actions that we anticipate will do the greatest good.” Experts say getting the unvaccinated their first shots remains the top priority, and the panel wrestled with whether the booster debate was distracting from that goal. All three of the COVID-19 vaccines used in the U.S. are still highly protective against severe illness, hospitalization and death, even with the spread of the extra-contagious delta variant. But only about 182 million Americans are fully vaccinated, or just 55% of the population. “We can give boosters to people, but that’s not really the answer to this pandemic,” said Dr. Helen Keipp Talbot of Vanderbilt University. “Hospitals are full because people are not vaccinated. We are declining care to people who deserve care because we are full of unvaccinated COVID-positive patients.” Thursday's decision represented a dramatic scaling back of the Biden administration plan announced last month to dispense boosters to nearly everyone to shore up their protection. Late Wednesday, the Food and Drug Administration, like the CDC panel, signed off on Pfizer boosters for a much narrower slice of the population than the White House envisioned. The booster plan marks an important shift in the nation's vaccination drive. Britain and Israel are already giving a third round of shots over strong objections from the World Health Organization that poor countries don't have enough for their initial doses. Read:‘Soul-crushing’: US COVID-19 deaths are topping 1,900 a day Walensky opened Thursday's meeting by stressing that vaccinating the unvaccinated remains the top goal “here in America and around the world.” Walensky acknowledged that the data on who really needs a booster right away “are not perfect.” “Yet collectively they form a picture for us,” she said, "and they are what we have in this moment to make a decision about the next stage in this pandemic.” The CDC panel stressed that its recommendations will be changed if new evidence shows more people need a booster. The CDC advisers expressed concern over the millions of Americans who received Moderna or Johnson & Johnson shots early in the vaccine rollout. The government still hasn’t considered boosters for those brands and has no data on whether it is safe or effective to mix-and-match and give those people a Pfizer shot. “I just don’t understand how later this afternoon we can say to people 65 and older, ‘You’re at risk for severe illness and death, but only half of you can protect yourselves right now,’” said Dr. Sarah Long of Drexel University. About 26 million Americans got their last Pfizer dose at least six months ago, about half of whom are 65 or older. It's not clear how many more would meet the CDC panel's booster qualifications. CDC data show the vaccines still offer strong protection against serious illness for all ages, but there is a slight drop among the oldest adults. And immunity against milder infection appears to be waning months after people's initial immunization. Read: Biden aims to enlist allies in tackling climate, COVID, more For most people, if you’re not in a group recommended for a booster, “it’s really because we think you’re well-protected,” said Dr. Matthew Daley of Kaiser Permanente Colorado. Public health experts not involved in Thursday’s decision said it is unlikely people seeking third doses at a drugstore or other site will be required to prove they qualify. Even with the introduction of boosters, someone who has gotten just the first two doses would still be considered fully vaccinated, according to the CDC's Dr. Kathleen Dooling. That is an important question to people in parts of the country where you need to show proof of vaccination to eat in a restaurant or enter other places of business. Among people who stand to benefit from a booster, there are few risks, the CDC concluded. Serious side effects from the first two Pfizer doses are exceedingly rare, including heart inflammation that sometimes occurs in younger men. Data from Israel, which has given nearly 3 million people — mostly 60 and older — a third Pfizer dose, has uncovered no red flags. The U.S. has already authorized third doses of the Pfizer and Moderna vaccines for certain people with weakened immune systems, such as cancer patients and transplant recipients. Other Americans, healthy or not, have managed to get boosters, in some cases simply by asking.

Transplant recipients and others with severely weakened immune systems can get an extra dose of the Pfizer or Moderna Covid-19 vaccines to better protect them as the Delta variant continues to surge, US regulators said Thursday. The late-night announcement by the Food and Drug Administration applies to several million Americans who are especially vulnerable because of organ transplants, certain cancers or other disorders. Several other countries, including France and Israel, have similar recommendations. It is harder for vaccines to rev up an immune system suppressed by certain medications and diseases, so those patients do not always get the same protection as otherwise healthy people – and small studies suggest for at least some, an extra dose may be the solution. "Today's action allows doctors to boost immunity in certain immunocompromised individuals who need extra protection from Covid-19," Dr Janet Woodcock, the FDA's acting commissioner, said. The FDA determined that transplant recipients and others with a similar level of compromised immunity can receive a third dose of the vaccines from Pfizer and Moderna at least 28 days after getting their second shot. The FDA made no mention of immune-compromised patients who received the single-dose Johnson & Johnson vaccine. The announcement comes as the extra-contagious Delta version of the coronavirus surges through much of the country, pushing new cases, hospitalisations and deaths to heights not seen since last winter. Read: Why might COVID-19 vaccine boosters be necessary? However, the FDA's decision only applies to this high-risk group, estimated to be no more than 3% of US adults. It’s not an opening for booster doses for the general population. Health authorities consider the extra dose part of the initial prescription for the immune-compromised. For example, France since April has encouraged that such patients get a third dose four weeks after their regular second shot. Israel and Germany also recently began recommending a third dose of two-dose vaccines. Separately, US health officials are continuing to closely monitor if and when average people's immunity wanes enough to require boosters for everyone – but for now, the vaccines continue to offer robust protection for the general population. The Centers for Disease Control and Prevention is expected to formally recommend the extra shots for certain immune-compromised groups after a meeting Friday of its outside advisers. Transplant recipients and others with suppressed immune systems know they are at more risk than the average American, and some have been seeking out extra doses on their own, even if it means lying about their vaccination status. The change means now the high-risk groups can more easily get another shot – but experts caution it is not yet clear exactly who should. "This is all going to be very personalised," cautioned Dr Dorry Segev, a transplant surgeon at Johns Hopkins University who is running a major National Institutes of Health study of extra shots for organ recipients. For some people, a third dose "increases their immune response. Yet for some people, it does not seem to. We do not quite know who is who yet." Read: Head of UN health agency seeks vaccine booster moratorium One recent study of more than 650 transplant recipients found just over half harboured virus-fighting antibodies after two doses of the Pfizer or Moderna vaccines – although generally less than in otherwise healthy vaccinated people. Another study of people with rheumatoid arthritis and similar autoimmune diseases found only those who use particular medications have very poor vaccine responses. There is little data on how well a third dose works, and if it causes any safety problems such as an increased risk of organ rejection. Wednesday, Canadian researchers reported that transplant recipients were more likely to have high levels of antibodies if they got a third dose than those given a dummy shot for comparison. Other small studies have similarly found that some transplant recipients respond to