(Reuters) – US Centers for Disease Control and Prevention on Friday supported a booster shot of the Pfizer and BioNTech COVID-19 vaccine for Americans age 65 and older, adults with underlying medical conditions and adults at high risk and institutional settings.
The decision by CDC chief Rochelle Walensky is in line with the US Food and Drug Administration's approval of the shot earlier this week and follows an August announcement of a broad reinforcement from her and other top US health officials.  The CDC recommendation cleared the way for booster shots to begin on Friday. One of the largest U.S. pharmacy chains, the Walgreens Boots Alliance, said on Friday that boosters were available directly to eligible individuals, and some states like Vermont said they would be available in their vaccination centers. They will also be rolled out in long-term care facilities.
Ms. Walensky's decision broke from a recommendation on Thursday by a group of experts from external advisers to the agency who had said that a narrower group of people should get the extra shot. The CDC Director is not obliged to follow the panel's advice.
The panel specifically excludes people in high-risk jobs and people in close living conditions on Thursday, partly due to concerns about a rare heart inflammation that has occurred mainly in younger men. They were also concerned that the recommendation would be too broad to be implemented effectively.
It recommended boosters for the elderly and some people with medical conditions that put them at higher risk for severe COVID-19.
Authorization opens boosters for more than 20 million people who received their second Pfizer shot more than six months ago.
The CDC on Thursday told its advisers that there would be no requirement for people to submit documentation to prove that they have underlying conditions or work in risk settings.
Researchers have disagreed about the need for COVID-19 vaccine enhancers, some of which from the FDA and the World Health Organization say there is insufficient evidence that they are needed by someone other than the elderly and that more people around the world need a first dose of the vaccine first.
Pfizer and US health officials have claimed that the shots prevent hospitalizations and deaths and that emerging data indicate that they can also slow down mild infections.
The highly transmissible Delta variant of the coronavirus has driven an increase in covid-19 cases in the United States, which peaked on September 1, and has since decreased by about 25% to just over 120,000 cases per day, based on a 7-day moving average.
Ms. Walensky said her agency had to make recommendations based on complex, often incomplete information.
"In a pandemic, even with uncertainty, we must take action that we expect will be most beneficial," she said in a statement.  "Anyone can show up"
SVB Leerink analyst Geoffrey Porges said he expects many of the "troubled wells" to seek booster shots in the coming weeks because of the CDC's resolve claims on who is eligible.
"It literally means that anyone can show up and say I're at increased risk of getting infected again," Porges said.
The United States had approved extra shots for those with weakened immune systems last month and about 2.3 million people have already received a third shot, according to the CDC.
Because the FDA has not yet considered the Mother's application for boosters and Johnson & Johnson has not yet applied for one, Pfizer is likely to benefit, he said.
Pfizer shares fell slightly on Friday, while Moderna shares fell more than 3%.
Bernd Salzberger, head of infection at Regensburg University Hospital in Germany, said that given the uncertainty about the durability of protection, experts could easily come to different conclusions about who should be eligible for boosters and when.
"The United States is currently undergoing a more serious wave of infections than here because there are many more unvaccinated in several states, mainly in the south. It may be a reason for someone to say that we must protect healthcare staff in particular, says Salzberger.
The CDC said that people 65 and older should get a boost and also recommended the images for all adults over the age of 50 with underlying diseases, such as cancer or diabetes.
It is said, based on individual benefits and risks, that 18- to 49-year-olds with underlying medical conditions can get a boost, and also people between 18 and 64 years with an increased risk of exposure and transmission due to occupational or institutional settings.
The CDC said that approximately 26 million people would now be eligible for a Pfizer / BioNTech booster, including 13 million 65 years or older.
William Schaffner, an infectious disease expert at Vanderbilt University Medical Center, said the images will be widely available under this policy.
"I'm skeptical that places will be overwhelmed, but there may be some places, especially in high-income areas, where they can get a lot of interested people," says Schaffner.