Prevalence, Trends and Conditions for the DTP3 Vaccine: A 25-Year Historical Perspective

The aim was to verify the prevalence of vaccination coverage, tendency and factors of the third dose of the vaccine against diphtheria, tetanus and pertussis-DTP3 in surveys over the period of 25 years in a state of the Northeast of Brazil.

Cross-sectional and temporal series, utilizing ad hoc database, were extracted from the Health and Nutrition State Research 1991, 1997, 2006 and 2015/2016. Children from 12 to 23 months of age with proof in the vaccination card were included. The vaccination coverage (outcome) of each year was calculated, the tendency throughout the period was analyzed and the associations through Pearson chi-squared were tested. The results of the first and last survey were compared with a significance level of 5%. The reasons of the crude prevalence and confidence intervals of 95% were estimated.

The vaccination coverage in 1991, 1997, 2006 and 2015/2016 was 77.6%, 82.7%, 89.7% and 72.9%, respectively, with an increasing tendency from 1991 to 2006 (p<0.001) and decreasing between 2006 and 2015/2016 (p<0.001). Factors in 1991: low socioeconomic conditions; lack of access to health service and pre-natal care, nutritional deficit and diarrhea in children (p<0.005). In 2015/2016, low socioeconomic conditions and diarrhea persisted and a larger family size, black, negative self-perception of happiness, both from the mother (p<0.05), were identified.

The factors of the recent decrease of vaccination coverage are complex, multifactorial, dependent of context and even on subjective aspects of the maternal perception. Its identification contributed to the understanding of inadequate vaccination at the state level.