Strict interpretation of vaccination guidelines with computerized algorithms and improper timing of administered doses

Background. Frequently changing immunization recommendations may lead to in correctly administered doses. Objective. To determine the incidence and characteristics of inappropriatel y timed vaccinations. Methods. Prospectively collected immunization histories of patients <5 year s old from well-child care encounters with pediatric residents in a large u rban clinic during a 3-month study period. New patients or those with no im munization history in the medical record were excluded. Paper records were verified before each visit and served as the immunization history. Immuniza tion records were entered into and analyzed by the Massachusetts Immunizati on Information System with strict interpretation of minimum spacing and age guidelines to identify invalid vaccine doses. Reasons for invalidity were determined by manual review. Invalid doses were cross-referenced with clini c schedule to determine who delivered doses. Results. Inclusion criteria were met by 690 encounters. Charts were availab le for review before the encounter for 580, containing 6983 total immunizat ions. Of these 289 (4.1%) administered doses were invalid; 206 of 580 (35.5 %) patients had at least one invalid dose. Common invalid doses given were unnecessary poliovirus vaccine around 18 months (n = 66) and second hepatit is B vaccine given too soon after the first (n = 53). All types of provider s gave invalid doses; pediatric residents and fellows delivered significant ly more (P < 0.01). Conclusions. By strict interpretation of immunization guidelines, many pati ents were immunized incorrectly. Clinicians should be aware of common error s in vaccine dosing and national guidelines should be simplified.