Abstract
OBJECTIVES: To determine whether missing the HepB birth dose vaccine is a risk factor for incomplete vaccination later in childhood. METHODS: This was a retrospective cohort study of infants born over one year at an academic medical center. The "not vaccinated at birth" group consisted of all infants who did not receive the HepB birth dose vaccine by seven days of life, while the "vaccinated at birth" group included infants who did receive the birth dose. The primary outcome was vaccination status at 18 months of age, determined from the state vaccination registry. RESULTS: Infants "not vaccinated at birth" had lower vaccination rates. At 18 months, 44% of the "vaccinated at birth" group received all recommended vaccines, compared with 23% of the "not vaccinated at birth" group (p < 0.001); at 24 months, rates were 65% and 45%, respectively (p < 0.001). Over 80% of the variability in vaccination completions were related to a single latent variable, which is most likely vaccine hesitancy/refusal. CONCLUSIONS: Infants who miss the HepB birth dose vaccine are at risk for under-immunization by 18 and 24 months of age. This suggests that parents likely form opinions about vaccines long before the birth of their child; therefore, efforts to influence attitudes must begin earlier.