The Effects of Perceived Disease Risk and Access Costs on Infant Immunization

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 immunizations. 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. This response is concentrated among low-socioeconomic status (SES) subgroups. In addition, we find that pertussis outbreaks increase the likelihood of immunization against other vaccine-preventable diseases. These spillover effects are almost as large the direct effects and are present only for vaccines that are typically given during the same visit as the pertussis vaccine, which suggests that healthcare access costs play an important role in parents' vaccination decisions