A practical method of securing data regarding services to mothers and infants.

Abstract

ARECENT analysis of the extent of immunization against diphtheria was made in the city of Philadelphia by a fairly simple sampling study. The method used, which appears to be of practical use to health officers, involved the direct interrogation of the mothers of all children in a specific group (defined in this instance as children aged 12 and 13 months) rather than a random sample. This age group was chosen because: (a) these children have all had a six months' opportunity to be protected by immunization by usual practice, and public health teaching stresses protection by this time, (b) the first birthday is a transition period from infant to preschool life in public health thinking and seems a reasonable time for check-up by public health services with respect to such items, (c) the mothers can still be expected to recall the details involved. Interrogation was done by (1) mailing a friendly questionnaire with a stamped, addressed return envelope, (2) telephone follow-up, (3) home visit. In 1948 there were 41,746 resident births in Philadelphia. It was decided that the births occurring in the two months one year previous to the study would provide a significant sample. February and March resident births were used which numbered 6,248 (illegitimate births and deaths removed) which is 15 per cent of the total resident births. The name of the child and the name and address of the mother and the race were obtained by using slips from an existing system whereby the Division of Child Health was notified of all births. It was necessary to go back to the death certificates to check these names against the infant deaths, but this step was considered very important as the names of several hundred deceased babies were removed.