C.D.C. Panel to Debate Boosters and ‘Mix-and-Match’ Strategy

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As the latest wave of the virus ebbs in most parts of the United States, advisers to the Centers for Disease Control and Prevention will meet on Thursday to evaluate which Americans need extra doses of the coronavirus vaccines made by Moderna and Johnson & Johnson.

They will also discuss the so-called mix-and-match strategy — whether people fully immunized with one company’s vaccine should be allowed to switch to a different one for their booster shot.

On Wednesday, the Food and Drug Administration authorized booster shots for millions of people who received the Moderna and Johnson & Johnson vaccines, just as it did for recipients of Pfizer-BioNTech shots last month. The F.D.A. also gave the green light for people eligible for boosters to get an extra dose of a different brand from the one they first received.

But in practice who will get the shots and when depends greatly on the C.D.C.’s final guidance. Though the agency’s recommendations do not bind state and local officials, they hold great sway in the medical community.

Regardless of the tenor of the discussion, the final recommendations from the C.D.C.’s panel — the Advisory Committee on Immunization Practices — are unlikely to hold surprises. The committee is expected to endorse additional doses of the vaccines for many Americans and to strive to bring the country closer to fulfilling President Biden’s promise to provide boosters to all adults.

It will not happen without some misgivings, however.

Some of the C.D.C.’s advisers last month voiced strong reservations about a booster of the Pfizer-BioNTech vaccine, saying the science did not support additional shots for anyone other than adults over 65. A majority voted to recommend booster shots for people with certain medical conditions that increase the risk of Covid-19.

The committee did not support boosters for people whose jobs expose them to the virus — but in a highly unusual move, Dr. Rochelle P. Walensky, the C.D.C.’s director, overturned their decision.

“It is going to be a difficult meeting, because I suspect that the science won’t have changed much,” said Dr. Sarah S. Long, a pediatrician and infectious diseases expert at Drexel University in Philadelphia. “I can see making it clear that we still don’t think this is the right approach, and Dr. Walensky would have to override it.”

A similar dynamic played out on the expert panel advising the F.D.A. at a meeting last week. Several advisers to the F.D.A. criticized the paucity of evidence supporting a Johnson & Johnson booster and expressed discomfort at having to decide on the booster before the F.D.A. had carefully vetted the data.

Still, they unanimously voted in favor of a second Johnson & Johnson shot for adults who had received that vaccine because it was clear that two doses would be more protective than one, according to one member of the panel, Dr. Paul A. Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia.

What to Know About Covid-19 Booster Shots

Who is eligible for a booster shot?

The F.D.A. has authorized booster shots for millions of recipients of the Pfizer-BioNTech, Moderna and Johnson & Johnson vaccines. Pfizer and Moderna recipients who are eligible for a booster include people 65 and older, and younger adults at high risk of severe Covid-19 because of medical conditions or where they work. Eligible Pfizer and Moderna recipients can get a booster at least six months after their second dose. All Johnson & Johnson recipients will be eligible for a second shot at least two months after the first.

Can I switch Covid vaccines for a booster?

Yes. The F.D.A. has updated its authorizations to allow medical providers to boost people with a different vaccine than the one they initially received, a strategy known as “mix and match.” Whether you received Moderna, Johnson & Johnson or Pfizer-BioNTech, you may receive a booster of any other vaccine. Regulators have not recommended any one vaccine over another as a booster. They have also remained silent on whether it is preferable to stick with the same vaccine when possible.

What underlying medical conditions qualify for a booster shot?

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 and current and former smokers are also eligible.

What occupations are eligible for boosters?

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; grocery store workers.

Can I get a flu shot at the same time as a Covid vaccine or booster shot?

Yes. The C.D.C. says the Covid vaccine may be administered without regard to the timing of other vaccines, and many pharmacy sites are allowing people to schedule a flu shot at the same time as a booster dose.

“There was a value to having that as a one-dose vaccine when it first came out,” Dr. Offit said. “But I think it was always on the road to being a two-dose vaccine.”

He and others suggested that people who got the Johnson & Johnson vaccine might be better served by getting a second dose of the Pfizer-BioNTech or Moderna vaccines. The F.D.A. on Wednesday updated its authorization of all three vaccines, which will allow the C.D.C.’s advisory committee to recommend this mix-and-match strategy when it meets on Thursday.

At last week’s meeting, the F.D.A. advisers were shown evidence indicating that switching between two vaccine types might produce a richer immune response than boosting with the same vaccine.

San Francisco has offered Pfizer-BioNTech or Moderna shots to Johnson & Johnson recipients since August, and many Americans who initially received the Johnson & Johnson vaccine have sought out booster doses of those vaccines on their own before federal agencies had endorsed them.

But the F.D.A. advisers could not vote to recommend that people who initially got the Johnson & Johnson vaccine follow it up with one of the mRNA vaccines because the F.D.A. did not give them that option.

“The formal vote was on the J.-&-J. booster following the J.-&-J. vaccine,” said Dr. Stanley Perlman, an immunologist and coronavirus expert at the University of Iowa. But “everybody knew that the data would show that the heterologous boost would be better.” (Heterologous refers to a shot of a different vaccine.)