Health cards, maternal reports and the measurement of immunization coverage: the example of Guatemala

Immunization against major childhood diseases has been an essential component of health policies in developing countries. However, despite its importance and the efforts invested by many organizations in promoting immunization programs, consistent and accurate measurement of immunization coverage has not yet been achieved. In this paper, we explore the implications of alternative methods of measuring immunization coverage rates in Guatemala, using data from the 1987 Encuesta Nacional de Salud Materno Infantil, and we consider the dangers of making inferences about levels and trends in coverage from cross-sectional data. The results indicate that (1) service statistics may well lead to overestimates of coverage; (2) survey estimates derived from health cards can also produce severely biased estimates; and (3) in spite of problems associated with maternal recall, mothers' reports of their children's vaccination status probably result in substantially improved estimates of immunization coverage.