Objectives: To assess the hepatitis B immunization rate and to identify the reasons for an incomplete immunization series in newborns and infants seen in primary care practices.
Design: An inception cohort study enrolling newborns and infants and assessing their hepatitis B immunization status at 9 and 18 months of age.
Setting: Six primary care offices, most in rural environments.
Patients: All newborns and infants seen at 1 of 6 offices.
Intervention: Infants born between January 1, 1993, and September 30, 1994, were followed up through June 30, 1995. Hepatitis B immunization status and the reasons for an incomplete status were recorded at each visit.
Main outcome measures: Hepatitis B immunization rates at 9 and 18 months of age, and the reasons for immunization failure.
Results: The immunization rates of infants aged 9 and 18 months were 60% and 77%, respectively. The most common reasons for inadequate immunization of the 247 infants followed up through age 18 months were patient transfer (7%), failing to return for a scheduled visit (4%), and guardians refusing the immunization (4%). Failure to return for a scheduled visit was the reason for the incomplete immunization in 13% of the 9-month-old infants. Immunization of these patients was the most important factor in the higher immunization rate at 18 months of age. By the age of 18 months, 95% of all infants had received at least 2 doses of the hepatitis B immunization.
Conclusions: A hepatitis B newborn immunization rate of 77% by age 18 months was achieved in a primary care office setting. Barriers to complete immunization by the age of 18 months include patient transfer, patient failure to return, and parental refusal of immunization.