Disease outbreaks, healthcare utilization, and on-time immunization in the first year of life

This paper examines the determinants of parental decisions about infant immunization. Using the exact timing of vaccination relative to birth, we estimate the effects of local pertussis outbreaks occurring in utero and during the first two months of life on the likelihood of on-time initial immunization for pertussis and other diseases. We find that parents respond to changes in perceived disease risk: pertussis outbreaks within a state increase the rate of on-time receipt of the pertussis vaccine at two months of age, particularly among low-socioeconomic status (SES) subgroups. In addition, we find that pertussis outbreaks increase the likelihood of immunization against other vaccine-preventable diseases. Spillover effects in low-SES subgroups are as large as direct effects and are present only for vaccines given during the same visit as the pertussis vaccine, which suggests that provider contact may be a key factor in infant vaccination decisions in poor families.