BACKGROUND: Maternal immunization with tetanus, diphtheria, and acellular pertussis (Tdap) vaccine confers protection to young infants. We aimed to describe trends in pertussis incidence and associated mortality in children aged <12 months before and after introduction of maternal Tdap immunization in Bogotá, Colombia.
METHODS: Data on pertussis-related cases/deaths in infants aged <12 months were collected from SIVIGILA for the period 2005-2016, and compared incidence for the pre-vaccine introduction (2005-2012) and post-maternal Tdap vaccination (2014-2016) periods in infants aged <12 months and in three distinct age-strata; ≤6 weeks, 7-<28 weeks, and 28-52 weeks. Mortality comparisons were performed in all infants <12 months.
RESULTS: From 2005 to 2016, 2315 laboratory or clinically-confirmed pertussis cases were reported in infants <12 months of age (278 cases in young infants aged ≤6 weeks); 55 pertussis deaths were reported in children aged <12 months. No pertussis deaths were reported in the 2014-2016 period. Since maternal Tdap introduction in 2013, a consistent decline in pertussis incidence and mortality was observed. In the time-series analysis, incidence declined from 209.4/100,000 persons (2005-2012) to 49.1/100,000 persons (2014-2016) in all children <12 months; a 87.5% (95%CI: 77.2-93.2%) reduction. For these same period's incidence in young infants ≤6 weeks declined from 196.7 to 89.6/100,000 person-years (an 54.4% [95% CI: 35.4-67.9%] reduction). Greater incidence reductions were observed in older infants; 73.4% (95% CI: 68.4-77.6%) in those aged 7-<28 weeks, and 100% in those aged 28-52 weeks. A 100% reduction in Pertussis mortality in infants <12 months was observed. Since Tdap introduction, maternal vaccine coverage rose from <60% in 2013-2015 to 80% in 2016.
CONCLUSIONS: Implementation of maternal immunization in Bogotá may have contributed to the reduction in pertussis incidence and mortality among infants <12 months of age.
