Rates of Missed MMR Vaccination Have Increased Since Pandemic

New research published by investigators in the Journal of the American Medical Association highlights a growing proportion of children who did not receive the measles, mumps, and rubella (MMR) vaccine by age 2 years, with the trend beginning after the COVID-19 pandemic. Furthermore, children who did not receive 2- and 4-month routine immunizations on time were significantly more likely to not receive any MMR vaccine by age 2.¹

Children Are Missing Their MMR Doses at Higher Rates Since the Pandemic

The cohort study examined infants with access to routine care within the first 2 months, first year, and second year of life. Truveta Data, an electronic health record database from a collective of health systems, was utilized. They were followed for 24 months to assess vaccination outcomes between January 2018 and April 2025. The primary outcome was determining timely, late, or no receipt of MMR by 2 years of age.¹

Across that period, 78.4% (n = 252,250) of children with regular access to care received their first MMR vaccination on time, according to Nina B. Masters, PhD, MPH, senior applied research scientist at Truveta and lead investigator of the study. Although the proportion of children who did not receive an MMR vaccine by 2 years of age was small, the rate increased from 5.3% in 2020 to 7.7% in 2024, an increase Masters described as “a worrying signal of ongoing vaccination decline.”^1,2

As they dove deeper into the cohort of children with late vaccination, Masters and her team found that children who received their 2-month immunizations late had 7 times greater odds of missing their MMR vaccination at 2 years (adjusted odds ratio [aOR], 6.96; 95% CI, 6.60-7.34). For children who received their 4-month immunizations late, they had 6 times greater odds of missing their age 2 MMR vaccination (aOR, 6.16; 95% CI, 5.84-6.50).^1,2

“This indicates that parents are expressing vaccine hesitancy and delay very early in their children’s lives, even as early as the first routine vaccine,” Masters explained. “The window for intervention—to engage parents about their hesitancy and provide more education about the safety and effectiveness of these vaccines—must happen very early.”²

Factors influencing a lack of vaccination for these children included being male (aOR, 1.12; 95% CI, 1.07-1.16), living in rural areas (aOR, 1.09; 95% CI, 1.03-1.15), living in areas of unknown urbanicity (aOR, 1.45; 95% CI, 1.18–1.79), and being non-Hispanic or Latino (aOR, 1.51; 95% CI, 1.41-1.61), among others. Children who adhered to the American Academy of Pediatrics’ recommended immunization schedule in the first 2 years of life were significantly more likely to receive timely MMR vaccination, according to the investigators.¹

Expert: What Pharmacists Should Know About MMR Vaccine Counseling

Masters explained that pharmacists play a critical role in facilitating vaccination discussions with parents and caregivers early, which can help build trust as their child navigates their care pathway. Although Masters acknowledged that this could be challenging in the beginning, especially as parents have yet to forge a strong bond with their child’s provider, pharmacists are in a key position to communicate the decades of research and real-world evidence that has solidified vaccination as a tenet of public health.^1,2

“When parents adhere to the recommended timetable for early vaccines, they are more likely to ensure their children receive all vaccinations to protect them from preventable disease,” Masters noted.²

It is especially important for early intervention, as Masters and her team found very early vaccine hesitancy expressed among parents and caregivers. Pharmacists can effectively counter misinformation by engaging with parents about any questions they may have regarding the safety and effectiveness of childhood immunizations, including MMR.²

“This new research shows that delayed or missed early vaccinations has a long-term impact on a child’s vaccine trajectory, which should further empower clinicians to engage earlier with parents and caregivers in an effort to address hesitancy, questions, and education,” Masters concluded.²

REFERENCES

1. Masters NB, Cartwright BMG, Rodriguez PJ, et al. Delayed or absent first dose of measles, mumps, and rubella vaccination. JAMA Netw Open. 2026;9(1):e2551814. doi:10.1001/jamanetworkopen.2025.51814

2. Nina B. Masters Interview With Pharmacy Times. Retrieved January 8, 2026. Accessed January 9, 2026.