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Delayed or Absent First Dose of Measles, Mumps, and Rubella Vaccination
Nina B Masters1, Brianna M Goodwin Cartwright1, Patricia J Rodriguez1
1Truveta Research, Truveta Inc, Bellevue, Washington.
Importance:
A total of 1723 measles cases have been reported as of November 12, 2025, in the US, reaching their highest levels since elimination in 2000. MMR (measles, mumps, and rubella) vaccination coverage has decreased, and factors associated with delayed and missed vaccination since the COVID-19 pandemic are not well explored.
Objectives:
To characterize coverage and trends of timely MMR vaccination and assess factors associated with late vaccination and nonvaccination by 2 years of age.
Design, Setting, And Participants:
In this cohort study, infants who accessed routine care within the first 2 months, first year, and second year of life were followed up for 24 months to assess vaccination outcomes between January 1, 2018, and April 30, 2025. Participants were children seeking care within Truveta Data, an electronic health record database from a collective of US health care systems.
Exposures:
Timely receipt of routine 2- and 4-month immunizations and adherence to the American Academy of Pediatrics well child visit schedule.
Main Outcomes And Measures:
The primary outcome was timely, late, or no receipt of MMR by 2 years of age. Associations with primary exposures and sociodemographic factors were modeled using mixed-effect logistic regression with state-level random effects. Models were stratified by pre- vs post-COVID-19 MMR eligibility, with results after the COVID-19 pandemic reported as primary.
Results:
In this study of 321 743 children (166 017 boys [51.6%]) with regular access to care, 78.4% (252 250 of 321 743) received their first MMR vaccination on time, increasing from 75.6% (12 840 of 16 978) in 2018 to 79.9% (39 739 of 49 767) in 2021, then decreasing to 76.9% (40 306 of 52 388) in 2024. The strongest factors associated with no MMR vaccination by 2 years was late administration of a child's 2-month vaccines (adjusted odds ratio [AOR], 6.96 [95% CI, 6.60-7.34]) and 4-month vaccines (AOR, 6.16 [95% CI, 5.84-6.50]).
Conclusions And Relevance:
In this cohort study of children with regular access to care, most received their MMR vaccine on time, but the proportion not receiving the MMR vaccine by 2 years of age has increased since the COVID-19 pandemic. Children who did not receive their 2- and 4-month vaccines on time were significantly more likely to not receive any MMR vaccine by 2 years, highlighting opportunities for intervention.
Insights
Measles, mumps, and rubella (MMR) vaccination rates declined post-COVID-19. Children with delayed 2- and 4-month immunizations were more likely to miss their MMR vaccine by age two.
Area of Science:
- Pediatric infectious disease epidemiology
- Public health surveillance
- Vaccine-preventable diseases
Background:
- Measles cases in the US are at their highest since 2000, with declining vaccination coverage.
- Factors influencing delayed or missed measles, mumps, and rubella (MMR) vaccinations post-COVID-19 pandemic require exploration.
Purpose of the Study:
- To analyze MMR vaccination coverage and trends.
- To identify factors associated with delayed or missed MMR vaccination by age two.
Main Methods:
- A cohort study followed 321,743 children for 24 months using electronic health records from US healthcare systems (January 2018 - April 2025).
- Vaccination outcomes were assessed against the American Academy of Pediatrics well-child visit schedule.
- Mixed-effect logistic regression modeled associations with sociodemographic factors and early vaccine receipt, stratified by pre- and post-COVID-19 eligibility.
Main Results:
- Overall, 78.4% of children received their first MMR vaccine on time, with coverage fluctuating between 2018-2024.
- A significant increase in the proportion of unvaccinated children by age two was observed post-COVID-19.
- Late administration of 2-month (aOR, 6.96) and 4-month (aOR, 6.16) vaccines were strongly associated with no MMR vaccination by age two.
Conclusions:
- Despite most children receiving timely MMR vaccination, a concerning rise in unvaccinated individuals by age two has emerged since the COVID-19 pandemic.
- Early-life vaccination timeliness, particularly for 2- and 4-month immunizations, is critical for ensuring complete MMR vaccination.
- Targeted interventions focusing on timely early childhood immunizations can improve overall MMR vaccine uptake.
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