The nurse completed 1-page forms and attached them to charts of children who might be eligible for immunization on that day’s visit. No form was completed for children who were up to date on immunizations. No chart review was performed that day on children in the control group, and no form was attached to the control group’s charts. The form acted as a prompt for the physician to ask the parent or guardian if the child had received the immunizations in question. If the physician determined there was a valid reason not to administer the vaccines on that visit, the physician noted the reason on the form and checked off the “Do not immunize” option on the form. If there were no contraindications to immunization, and if the parent or guardian gave informed consent for immunization, the physician checked off the “Immunize” option.
Evaluation of intervention
Review of records for all eligible children seen during the study period began in October 1996 and continued through January 1997. All reviews were done at the clinic using a laptop computer for direct entry into an onscreen data entry form. The chart reviewer was blinded as to intervention or control status. The data collected included (1) child’s name; (2) record number; (3) date of birth; (4) dates of vaccine administration for hepatitis B (HEPB),diphtheria/tetanus/pertussis (DTP), oral polio vaccine (OPV), Haemophilus influenzae type B (HIB), and measles/mumps/rubella (MMR); (5) dates of clinic visits within the study period; (6) dates of canceled appointments within the study period; and (7) dates of appointments not canceled and not attended within the study period. The principal investigator (I.T.B.), blinded to control or intervention status, then assessed the completeness of immunization for all vaccines recommended by the 1995 Recommended Childhood Immunization Schedule based on the child’s age at the end of the study period.
Statistical methods
Chi-square tests were used to test for association between on-time vaccination status and intervention-versus-control group membership. To test for a possible difference in mean age between the 2 groups, a t-test was performed. On-time vaccination for DTP3 was defined as vaccination occurring between the ages of 3.5 months (the earliest age at which properly spaced vaccinations could be accomplished) and 7 months (ie, from the day of the 3.5-month birthday to the day the child turned 7 months old). On-time vaccination for DTP4 was defined as vaccination occurring between the ages of 12 and 19 months (ie, from the day of the first birthday to the day the child turned 19 months old). For MMR1, on-time vaccination was defined as vaccination occurring between the ages of 12 and 16 months; for HEPB3, between the ages of 5.9 and 19 months (HEPB3 is not recommended before 6 months of age, but immunization 2 to 3 days early is still likely to be immunogenic); and for OPV3, between the ages of 3.5 and 19 months. On-time vaccination for DTP5 and OPV4 was defined as vaccination occurring between then ages of 4 and 7 years (ie, from the day of the 4-year birthday to the day the child turned 7 years old).
Analyses of on-time vs not-on-time vaccination for DTP3, DTP4, DTP5, MMR1, HEPB3, OPV3, and OPV4 were performed within the subgroups of children who were eligible to receive the vaccine during the study period. All analyses were performed using SAS software (SAS Institute Inc, Cary, NC).
Immunizations
DTP.Children considered eligible for DTP3 immunization had not yet been immunized with DTP3 before the beginning of the study period; had been immunized with DTP2 by 3 months before the end of the study period; and were at least 3.5 months old by 1 month before the end of the study. Children considered eligible for DTP4 immunization had not yet been immunized with DTP4 before the beginning of the study; had been immunized with DTP3 by 7 months before the end of the study period; and were at least 12 months old by 1 month before the end of the study. Children considered eligible for DTP5 immunization had not yet been immunized with DTP5 by the beginning of the study; had been immunized with DTP4 before age 4 years; and were at least 4 years old by 1 month before the end of the study period.
MMR. Children considered eligible for MMR1 immunization had not yet been immunized with MMR1 by the beginning of the study and were at least 12 months old by 1 month before the end of the study.
HEBP. Children considered eligible for HEPB3 immunization had not yet been immunized with HEPB3 before the beginning of the study; had been immunized with HEPB2 by 3 months before the end of the study period; and were at least 5.9 months old by 1 month before the end of the study.