Vaccine. 2016 Dec 7;34(50):6223-6228. doi: 10.1016/j.vaccine.2016.10.081. Epub 2016 Nov 12.
Vizzotti C1, Juarez MV2, Bergel E3, Romanin V2, Califano G2, Sagradini S2, Rancaño C2, Aquino A2, Libster R4, Polack FP5, Manzur J2.
Pertussis disease is a growing concern for developing countries. In Argentina, rates of illness and death peaked in 2011. More than 50% of fatalities due to pertussis occurred in infants younger than two months of age, too young for vaccination. In 2012, the government offered immunization with a vaccine containing Tdap to all pregnant women after 20weeks of gestation with the intent of reducing morbidity and mortality in young infants.
Maternal acellular pertussis vaccine impact on reducing infant disease burden was estimated based on data from the Argentinean Health Surveillance System. We divided Argentinean states in two groups experiencing high (>50) and low (⩽50) Tdap vaccine coverage and compared these two groups using a Bayesian structural time-series model. Low coverage regions were used as a control group, and the time series were compared before and after the implementation of the Tdap program.
We observed a relative reduction of 51% (95% CI [-67%, -35%]; p=0.001) in pertussis cases in high coverage states in comparison with the low coverage areas. Analysis of infants between two and six months showed a 44% (95% CI [-66%, -24%]; p=0.001) reduction in illness. Number of deaths was highest in 2011 with 76 fatalities, for an incidence rate of 2.9 per 100,000. Comparing with 2011, rates decreased by 87% to 10 subjects, or 0.9 per 100,000 in 2013.
We show an age-dependent protective effect of maternal Tdap immunization in a developing country for infants younger than six months.
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