Estimating vaccination coverage using parental recall, vaccination cards, and medical records

Objective. To compare estimates based on vaccination cards, parental recall . and medical records of the percentages of children up-to-date on vaccinat ions for diphtheria, tetanus, and pertussis; polio; and measles, mumps, and rubella. Method. The authors analyzed parent interview and medical records data from the Baltimore Immunization Study for 525 2-year-olds born from August 1988 through March 1989 to mothers living in low-income Census tracts of the ci ty of Baltimore. Results, Only one-third of children had vaccination cards; based on medical records, these children had higher up-to-date coverage at 24 months of age than did children without cards. For individual vaccines, only, two-thirds of parents could provide information to calculate coverage rates; however, almost all provided enough information to estimate coverage for the primar y series. For each vaccine and the series, parental recall estimates were a t least 17 percentage points higher than estimates from medical records, Fo r children without vaccination cards whose parents could not provide covera ge information, up-to-date rates based on medical records were consistently lower than for children with cards or with parents who provided coverage i nformation. Conclusions. Population-based vaccine coverage surveys that rely on vaccina tion cards or parental recall or both may overestimate vaccination coverage .