2762. A Cohort Analysis of Completion of the Pediatric Measles-Mumps-Rubella-Varicella Series in the United States

BACKGROUND: Since 2006, the recommended US vaccination schedule has included combination Measles-Mumps-Rubella (MMR) vaccine and separate Varicella (V) vaccine administered as first dose between 12–15 months, and second dose between 4–6 years, administered either separately or as a combination MMRV vaccine. Vaccine coverage alone does not provide information on the timeliness of vaccine receipt, a critical step in ensuring optimal protection, thus, we sought to evaluate overall series completion rates and identify factors related to under-vaccination. METHODS: A cohort of children born between 2006 and 2010, with continuous enrollment from birth to age 7 in the MarketScan® Commercial Claims and Encounters Database was studied. The administration of first and second doses of MMR- and V-containing vaccines was evaluated. Administration timeliness was categorized as recommended, acceptably early (prior to age 4 for the second dose), late (after the recommended time period), invalid, or missing at least one vaccine. A logistic regression analysis evaluated factors associated with under-vaccination. RESULTS: Among the 104,999 children included, 55.9% were vaccinated within the recommended time periods for both first and second doses, with timeliness higher for the second dose (80.1%) than the first dose (63.5%). By age 4, 20.1% of children were missing the first dose of either MMR or V (or both) and by age 7, 26.6% of children were missing at least one dose, with 9.4% missing all required vaccines. Factors associated with missed or delayed vaccination included geographic region, vaccination by a provider other than a pediatrician, and, for the second dose, having missed or delayed the first dose. Having additional children in the family was associated with a higher likelihood of missed or delayed vaccination for the first dose, but with a lower likelihood of missed or delayed vaccination for the second dose. CONCLUSION: About one in four children were missing at least one dose of MMR or V by age 7, indicating vaccine coverage is below Healthy People 2020 95% target. Additionally, delays in administration of the first dose indicate a potential for the development of cohorts of susceptible children large enough to sustain outbreaks. Strategies for addressing timeliness of vaccine receipt should incorporate factors associated with under-vaccination. [Image: see text] [Image: see text] [Image: see text] DISCLOSURES: All authors: No reported disclosures.