Missing First MMR Shot Most Significant Predictor of Nonvaccination by Age 2 Years

WEDNESDAY, Jan. 7, 2026 (HealthDay News) — Late administration of the 2- and 4-month measles, mumps, and rubella (MMR) vaccines is the strongest factor associated with no MMR vaccination by age 2 years, according to a study published online Jan. 2 in JAMA Network Open.

Nina B. Masters, Ph.D., M.P.H., from Truveta Inc. in Bellevue, Washington, and colleagues characterized coverage and trends of timely MMR vaccination and assessed factors associated with late vaccination and nonvaccination by age 2 years. Infants who accessed routine care within the first two months, first year, and second year of life were followed for 24 months to examine vaccine outcomes; data were included for 321,743 children with regular access to care.

The researchers found that 78.4 percent of the children received their first MMR vaccination on time, with an increase seen from 75.6 percent in 2018 to 79.9 percent in 2021, followed by a decrease to 76.9 percent in 2024. Late administration of a child”s 2-month and 4-month vaccines was the strongest factor associated with no MMR vaccination by age 2 years (adjusted odds ratios, 6.96 and 6.16, respectively).

“This study of children with regular access to care shows that childhood vaccine coverage and timeliness have been decreasing since the COVID-19 pandemic and that staying on the vaccine schedule early is the factor most associated with receiving a timely MMR vaccine, the best protection against the measles outbreaks that are spreading rapidly across the U.S.,” the authors write.

All study authors disclosed ties to Truveta, which funded the study; one author also disclosed ties to Eli Lilly.

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