Study shows how toxic RFK Jr.’s change to measles vaccine is for US toddlers

With no new data or clear reasoning, a panel of advisors hand-selected by anti-vaccine Health Secretary Robert F. Kennedy Jr. voted last September to strip federal recommendations for a combination shot against measles, mumps, rubella, and varicella (chickenpox). An analysis published today by independent researchers does the work the advisors neglected to do before the vote and, in turn, shows how harmful the decision is to vulnerable US toddlers.

The decision last fall followed clumsy discussion by Kennedy’s dubiously qualified advisors, which make up the Advisory Committee on Immunizations Practices (ACIP) for the Centers for Disease Control and Prevention. Most noticeably, their unprompted review of the MMRV vaccine did not include a standard decision-making framework ACIP has historically used to comprehensively evaluate what the change would mean for US children in practice—including basic questions, such as which children would be affected.

Still, the decision meant that private health insurance providers would no longer be required to cover the vaccine, called MMRV. It also meant the shot would no longer be available through a federal program that provides vaccines to about half of American children, mostly from low-income families.

The study published today in JAMA Network Open set out to assess who was using MMRV before the change. It was done by researchers in Washington state, who examined use of MMRV between 2015 and 2025 in King County, which encompasses Seattle. Reviewing immunization records of over 200,000 toddlers and young children ages 12 to 47 months, they found that a little over 31,000 children got the MMRV in that time period, about 15 percent.

MMRV vs MMR+V

This matches what was already known about the vaccine’s use—about 15 percent of kids nationwide get the shot, a small percentage. Most children instead receive a measles, mumps, and rubella shot (MMR) and a separate vaccine against varicella (chickenpox). Usually, the two vaccines are given at the same time, and the co-administration is abbreviated as MMR+V.