A dynamic, multi-level analysis of recent immunization trends in Colombia

During 1985-91, Latin American ministries of health carried out the ultimately successful Regional Polio Eradication Initiative. Unprecedented vaccine coverage levels were attained through a combination of mass campaigns, house-to-house vaccinations, and improvements in routine immunization services. Little is known, however, about the effects of these interventions on immunization demand; whether they reached so-called high-risk households and, if so, whether program effects were sufficient to offset the household risk factors. This paper examines the probability and timing of full immunization over this period in one case country, Colombia. Information on the immunization status of 3,609 vaccine-eligible children born 1985-90 was extracted from Colombia's 1990 Demographic and Health Survey. Annual immunization coverage estimates from the Colombian Ministry of Health for 1985-90 for 148 sample municipios were appended to each child record, along with household-level data. Initial non-parametric regressions showed that five of six observed risk factors negatively influenced full immunization probability. Multivariate logit models showed that parents who had already lost a child were significantly less likely to obtain immunization cards (a proxy for exposure to the routine immunization program), despite rising cardholdership rates over the period. Among 1,376 immunization cardholders, waiting times to full immunization fell monotonically over the period. Local program coverage of 80 per cent or higher and prior use of prenatal services both increased the probability of full immunization. However, three of five maternal occupational categories decreased the probability, as did three of six observed household risk factors. The results show that demand for routine immunizations rose over the period, that only the highest-risk households were not exposed to the routine program, and that routine program participation partially offset negative risk factor effects on the probability of full immunization. While targeted PHC interventions may increase health production by recruiting high-risk households into the routine PHC services, further health production increases will require more intensive follow-up of such households through routine PHC services.