984. Maternal and Infant Factors Influencing Influenza Vaccination Among Young Children Born in Colorado From 2008 to 2016

BACKGROUND: Factors influencing influenza vaccination in the first 2 years of life are important to identify and target strategies to increase vaccination rates, since this group is at high risk of morbidity from influenza. The objectives of our study were to determine maternal and neonatal factors associated with influenza vaccination in the first 2 years of life. METHODS: We conducted a retrospective cohort study using linked data from the Colorado Birth Registry Database and the Colorado Immunization Information System of live births between 2008 and 2016. Our population was limited to singleton, first births with first varicella vaccination documented in the immunization registry. Our primary outcome was receipt of at least one influenza vaccination in children ≤2 years. Exploratory variables included maternal (number of prenatal visits, urban vs. rural residence) and infant factors (term birth, admission to neonatal intensive care [NICU] at birth). Multivariable logistic regression was used to assess the association between these factors and influenza vaccination. RESULTS: Among 126,763 births in the cohort, 50.2% were vaccinated against influenza by 2 years of age. Mothers of unvaccinated children were older (27 vs. 26 years), married (67.8% vs. 66.8%), and more likely to have at least some college education (25.4% vs. 24.1%). A higher proportion of infants admitted to the NICU or who received oxygen were unvaccinated compared with vaccinated (8.5% vs. 8.0% and 2.5 vs. 2.1, respectively), P < 0.001 for all. There were no differences between urban vs. rural residence. In adjusted/stratified analyses, an increase in pre-natal visits was associated with a decrease in early influenza vaccination (IR = 0.992, 95% CI 0.986– 0.998, P = 0.0084 for Hispanic mothers and IR = 0.984, 95% CI 0.973–0.996, P = 0.0069 for non-Hispanic mothers). After adjusting for maternal age, preterm birth, and oxygen at birth, children admitted to the NICU were less likely to be vaccinated (IR = 0.915, 95% CI 0.873–0.959) against influenza by 2 years. CONCLUSION: There were statistically significant differences in maternal and neonatal factors between unvaccinated and vaccinated children with influenza in the first 2 years of life, but the differences were too small to be clinically significant. Ongoing studies are needed to devise strategies to target early influenza vaccination. DISCLOSURES: S. Rao, GSK: Investigator, Research grant.