A CDC advisory panel voted Thursday to limit the availability of a combined shot for measles, mumps, rubella and varicella, the virus that causes chicken pox for children.
The panel also delayed a vote on the newborn hepatitis B shot until Friday.
The 12-person Advisory Committee on Immunization Practices was chosen by Health Secretary Robert Kennedy Jr., who has expressed skepticism about the efficacy of vaccines.
The panel voted 8-3 with one abstention to recommend against giving the MMRV vaccine to children before the age of 4 over possible seizure concerns. Instead, the panel said MMR and chickenpox shots should be given separately.
Doctors say parents prefer the combined shot to limit the number of injections their child receives.
The vote may allow for health insurers to no long