Improving Childhood Vaccination Coverage: Understanding Maternal and Infant Characteristics Associated with Receipt of Hepatitis B and Other Recommended Vaccinations

Abstract

Vaccines are one of the most successful public health measures in modern medicine. Each year, thousands of illnesses, hospitalizations and deaths are directly prevented through immunization and indirectly through herd immunity. Paradoxically, vaccines have been so effective at preventing childhood diseases that a growing number of U.S. parents now question whether vaccination is necessary and whether perceived vaccine risks outweigh the benefits. In an era when few parents have firsthand experience with many of the diseases that vaccines prevent, new approaches are needed to maintain and increase vaccination coverage. Despite the rapid decline of vaccine preventable diseases (VPDs) in the U.S. these diseases are still common worldwide and will quickly resurface if vaccination rates are not maintained, as evidenced by recent outbreaks of pertussis and measles. Hepatitis B (HepB) is the first vaccine on the U.S. Childhood Immunization Schedule, which recommends seven shots (known as the 7-vaccine series) by 19 months of age. A HepB vaccine birth dose is recommended within 24 hours of birth for all medically stable infants born weighing at least 2000 grams and is the only vaccine recommended before the second month of age. We hypothesized that a missed HepB birth dose, accompanied by specific maternal and infant characteristics, could serve as a “red flag” to identify newborns who may be at high risk for missing subsequent childhood vaccines and could benefit from early, targeted interventions. Using a sample of infants born in Washington state between 2008 and 2013, this dissertation investigates predictors of the HepB birth dose (Aim 1), whether receipt of the HepB birth dose is associated with completing other recommended vaccines by 19 months (Aim 2) and whether timely HepB vaccine receipt, in conjunction with select maternal and infant characteristics, can be used to predict the risk of missing future childhood vaccinations (Aim 3). In Aim 1, we found that populations which are typically underserved (e.g., publicly insured, racial/ethnic minorities) were the most likely to receive the HepB birth dose, while infants who were non-Hispanic white, privately insured, and/or had an English-speaking mother were less likely to be vaccinated. Aim 2 showed that receiving the HepB birth dose was strongly associated with completing the 7-vaccine series by 19 months. In Aim 3, we developed and validated a risk prediction model which reliably identified newborns at risk for low completion of the 7-vaccine series by age 19 months. The results of our research suggest that the risk for low vaccination coverage is not evenly distributed in the population and that specific sociodemographic, clinical and birth hospitalization characteristics may indeed be associated with, and potentially predict, individual vaccine uptake. Further, receiving HepB during the birth hospitalization emerged as a key indicator of parental vaccine acceptance. The combined study findings serve as an important foundation for research focused on barriers to vaccine receipt in key subpopulations, and highlights areas for future interventional research in healthcare settings aimed at increasing childhood vaccination coverage.