MMRV policy change may leave vulnerable toddlers with fewer vaccine options
A JAMA Network Open analysis found MMRV use in King County was concentrated among children more likely to rely on free vaccines and safety-net clinics.
By Hana Yoshida · Markets Reporter
3 min read
A new analysis in JAMA Network Open says a federal decision to end recommendations for the combined MMRV shot could fall hardest on low-income and minority toddlers. Researchers in Washington state found that children who received the four-disease vaccine were more likely to depend on free vaccine programs and safety-net clinics.
The Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices voted last September to remove federal recommendations for the combined measles, mumps, rubella and varicella vaccine, known as MMRV. According to Ars Technica, the change meant private insurers would no longer be required to cover the shot and that it would no longer be available through a federal program that supplies vaccines to about half of U.S. children, many from low-income families.
The JAMA Network Open study examined immunization records from King County, Washington, which includes Seattle. Researchers reviewed records for more than 200,000 children ages 12 to 47 months between 2015 and 2025, and found that a little more than 31,000 children, or about 15%, received MMRV.
That share matched national patterns cited in the study. Most children instead receive the measles, mumps and rubella vaccine along with a separate chickenpox vaccine, a pairing often described as MMR+V.
Why the combined shot has been a secondary option
The Food and Drug Administration approved MMRV in 2005. Earlier analyses later found a small increase in febrile seizures when the combined vaccine was used as the first dose in children 12 to 15 months old, compared with giving MMR and varicella shots separately.
Those analyses found 7 to 8.5 seizure cases per 10,000 first-dose MMRV vaccinations, compared with 3.2 to 4.2 cases per 10,000 first-dose MMR+V vaccinations. The difference amounted to one additional febrile seizure for every 2,300 to 2,600 children vaccinated with MMRV, according to the prior research cited by Ars Technica.
Febrile seizures are associated with fever and can occur after common childhood illnesses, including flu or ear infections. Ars Technica reported that children almost always recover without lasting effects, and that about 5% of children have had a febrile seizure from some cause by age 5.
Because of the higher seizure rate, ACIP in 2009 preferred MMR+V for young children’s first dose while leaving MMRV available as an option for parents and doctors. Ars Technica reported that no new evidence has changed the view among experts that MMRV is safe and effective.
Study points to access concerns
The King County researchers found that MMRV use remained near 15% across the decade they studied. The children receiving it as a first dose were more likely than other vaccinated children to be from minority racial and ethnic groups, according to the JAMA Network Open analysis.
The study also found that MMRV recipients were more likely to be getting catch-up vaccination after the usual 12-to-15-month window, between 16 and 47 months. Compared with other vaccinated children, they were more than three times as likely to be eligible for a federal free-vaccine program and nearly four times as likely to be vaccinated at a safety-net clinic.
The researchers concluded that this group “might be at risk of not receiving recommended vaccines if options become limited.”
In a commentary published with the study, AcademyHealth policy experts Elizabeth Cope and Aaron Carroll criticized ACIP for acting without analyses of who used the vaccine. They wrote that the findings were “not surprising,” because combination vaccines can reduce injections, visits and cost barriers for families with less flexibility around work and follow-up care.
Cope and Carroll noted that the study covered one county in one state. They said similar patterns in areas with fewer resources could carry greater equity concerns, and wrote that several safeguards meant to protect ACIP’s independence were absent at the same time.
This story draws on original reporting from Ars Technica.