Predictors of late starters—babies that receive their first immunization after 90 days old—include fewer prenatal care visits, younger maternal age, higher birth order and receiving care at public health clinics. Policy-makers could leverage this information to improve patient outreach and outcomes.

Babies that do not initiate office-based immunizations before 90 days of age are at higher risk for becoming infected with childhood diseases preventable by vaccines. This retrospective cohort study identified maternal, provider and community predictors among late starters. Study included infants born in Philadelphia from January 2002 to December 2004 (N = 65,519).

Key Findings:

• Of the infants studied, 12.6 percent were late starters.
• Infants whose mothers were younger, received less than five prenatal visits, had less than a high school education, had more than two children and who smoked cigarettes prenatally were significantly more likely to be late starters.
• Practice type (hospital/university-based or public health clinics compared to private pediatrician’s offices) was also independently associated with the likelihood of being a late starter.
• Neither distance between infant’s residence and practice, nor neighborhood socioeconomic indicators, was independently associated with the outcomes.

Risk factor profiles based on information collected at birth can be used to identify higher-risk infants. Early intervention, such as partnering with prenatal care providers to create outreach plans, may be key strategies for preventing underimmunization.