ATLANTA — U.S. Health Secretary Robert F. Kennedy Jr.’s hand-picked vaccine advisory committee on Thursday recommended the Centers for Disease Control and Prevention adopt new restrictions on a combination shot that protects against chickenpox as well as measles, mumps and rubella.

The panel advised that the vaccine known as MMRV not be given before age 4 and that children in this age group instead get separate vaccines — one against MMR and another for varicella, or chickenpox. The vote was 8-3, with one member abstaining.

The Advisory Committee on Immunization Practices put off an expected vote on hepatitis B shots given to infants on the day they are born. On Friday — when it also takes up COVID-19 shots — it’s expected to decide whether to recommend that some babies can wait a month for those shots.

The committee makes recommendations to the CDC director on how already-approved vaccines should be used. CDC directors have almost always accepted those recommendations, which are widely heeded by doctors and guide vaccination programs.

Public health experts worry the votes will raise unwarranted concerns among parents. Kennedy, a leading antivaccine activist before becoming the nation’s top health official, has made or proposed numerous changes to the nation’s vaccine system, including firing the entire 17-member panel earlier this year and replacing it with a group that includes several anti-vaccine voices.

Experts are also concerned the panel’s actions could narrow access to the vaccines. The group voted 8-1, with three abstentions, to keep MMRV covered for kids as young as 12 months under the Vaccines for Children program, which pays for about half the shots given to kids in the U.S.

Several committee members expressed confusion during that follow-up vote on whether to align payments under the program with the more restrictive vaccine guidance they had just passed. Another federal official noted that there are other government insurance programs, including Medicaid, that will need to stop paying for that early combo dose.

Discussions on the MMRV vaccine focused largely on rare instances of feverish seizures associated with the first dose that is currently given to kids between ages 1 and 2.

Committee member Dr. Cody Meissner said such seizures may be “a very frightening experience” for families, but medical experts agree they’re not linked to brain function or school problems.

The panel last dealt with the issue in 2009, when it said either the combination shot or separate MMR and varicella shots were acceptable for the first dose, but that separate doses were generally preferred. Today, 85% of kids receive separate doses for the first round, according to information presented at the meeting.

Some doctors and public health experts say they are not aware of any new safety data that would explain the revisiting of those vaccination recommendations — and, in fact, many of the studies discussed Thursday were more than a decade old.

Dr. Richard Haupt, a vice president at Merck, which makes the MMRV vaccine ProQuad, said it’s been evaluated through clinical trials and post-approval studies, and the slight increase in feverish seizures after the first dose led to current CDC recommendations. Combination vaccines improve completion and on-time vaccination at a time when the nation is seeing a troubling decline in vaccination coverage, he said.

“Considering these trends, any policy decision that compromises the clarity or consistency of vaccination guidance … has the potential to further diminish public confidence,” he told the committee.

Dr. Mysheika Roberts, health department director in Columbus, Ohio, said one of the benefits of the combined vaccine is it limits the number of shots a child gets, which is useful in certain populations of patients, such as newly arrived immigrants who need lots of vaccines at the same time.

But she also acknowledged concerns about feverish seizures among children under age 4 and said, “maybe the guidance needs to be tweaked a little bit on that.”