The Food and Drug Administration is planning to allow Americans to receive a different Covid-19 vaccine as a booster than the one they initially received. Per the New York Times, this move could reduce the appeal of the Johnson & Johnson vaccine and provide flexibility to doctors and other vaccinators. The government would not recommend one shot over another, and the government might officially note that using the same vaccine as a booster when possible is preferable. State health officials have been requesting for weeks that vaccine providers could use their discretion to offer a different brand. Researchers presented the findings of a federally funded “mix and match” study to an expert committee that advises the Food and Drug Administration. The results of the study found that recipients of Johnson & Johnson’s single-dose shot who received a Moderna booster saw their antibody levels rise 76-fold in 15 days, compared with only a fourfold increase after an extra dose of Johnson & Johnson. Federal regulators this week are aiming to greatly expand the number of Americans eligible for booster shots. The F.D.A. is expected to authorize boosters of the Moderna and Johnson & Johnson vaccines by Wednesday (October 20) evening. The agency last month authorized booster shots of the Pfizer-BioNTech vaccine for at least six months after the second dose. The study suggested that Johnson & Johnson recipients might benefit most from a booster shot of the Moderna vaccine. A shot of the Pfizer-BioNTech vaccine also raised the antibody levels of Johnson & Johnson recipients more than Johnson & Johnson did, the study found, although not as much as Moderna did. The federal government will cover the cost of a different vaccine as a booster only if the F.D.A. authorizes the approach, officials said. Regulators are expected to authorize a booster of Moderna’s vaccine about six months after the second shot. Johnson & Johnson is headed for a booster shot of its vaccine at least two months after the first dose. Just over 15 million people have been fully vaccinated with Johnson & Johnson’s vaccine, compared with 69.5 million for Moderna’s and 104.5 million with Pfizer-BioNTech’s. The F.D.A. authorized booster shots for a select group of people who received their second doses of the Pfizer-BioNTech vaccine at least six months before. That group includes: vaccine recipients who are 65 or older or who live in long-term care facilities; adults who are at high risk of severe Covid-19 because of an underlying medical condition; health care workers and others whose jobs put them at risk; people with compromised immune systems are eligible for a third dose of either Pfizer or Moderna four weeks after the second shot. Regulators have not authorized booster shots for recipients of Moderna and Johnson & Johnson vaccines yet. The C.D.C. has said the conditions that qualify a person for a booster shot include: hypertension and heart disease; diabetes or obesity; cancer or blood disorders; weakened immune system; chronic lung, kidney or liver disease; dementia and certain disabilities; pregnant women; current and former smokers. The F.D.A. authorized boosters for workers whose jobs put them at high risk of exposure to potentially infectious people. The C.D.C. says that group includes: emergency medical workers, education workers, food and agriculture workers, manufacturing workers, corrections workers, U.S. Postal Service workers, public transit workers and grocery store workers.