Impact of the sequential poliovirus immunization schedule: a demonstration project

Objective: Researchers for this project evaluated compliance with the sequential poliovirus immunization schedule that uses inactivated poliovirus vaccine (IPV) for the first 2 doses of the polio immunization series, and assessed immunization coverage rates before and after implementation of this schedule at 6 public health clinics serving 1 county in Georgia. Design: Immunization histories for 3 birth cohorts of infants were compared: (1) the baseline cohort, born January 1 through June 30, 1995; (2) the evaluation cohort, born January 1 through June 30, 1997, after implementation of the schedule change; and (3) the dose-3 cohort, born August 1 through November 30, 1996 (i.e., old enough to be eligible for a third dose of poliovirus vaccine following implementation of the sequential schedule). Results: Following implementation of the new poliovirus immunization recommendations, 94% (534 of 567) of infants who received their first dose of poliovirus vaccine by age 3 months received IPV. Among these infants, 99.6% (532 of 534) were also up to date (UTD) for first doses of diphtheria and tetanus toxoids and acellular pertussis vaccine (DTP1/DTaP1), 99.6% (532 of 534) were UTD for first doses of hemophilus influenza type b (Hib 1), and 98.6% (527 of 534) had received at least one dose of Hepatitis B. Among infants visiting the clinics for their first or second dose of poliovirus vaccine, DTaP/DTP, and/or Hib, 76% received 3 or 4 simultaneous injections. In the dose-3 cohort, 78% (145 of 185) of infants who received a third dose of poliovirus vaccine had received 2 doses of IPV and 1 dose of oral poliovirus vaccine. Conclusions: Compliance with the recommended use of IPV for the first 2 poliovirus immunization doses as part of the sequential schedule was very high in this low-income and ethnically diverse population. Furthermore, the need for additional injections did not impede the delivery of recommended childhood immunizations.