Vaccine. 2016 Dec 7;34(50):6223-6228. doi: 10.1016/j.vaccine.2016.10.081. Epub 2016 Nov 12.

Impact of a maternal immunization program against pertussis in a developing country

Vizzotti C¹, Juarez MV², Bergel E³, Romanin V², Califano G², Sagradini S², Rancaño C², Aquino A², Libster R⁴, Polack FP⁵, Manzur J².

Author information

• ¹Dirección Nacional de Control de Enfermedades Inmunoprevenibles (DiNaCEI), Ministerio de Salud de la Nación, Argentina. Electronic address: cvizzotti@dicei.msal.gov.ar.
• ²Dirección Nacional de Control de Enfermedades Inmunoprevenibles (DiNaCEI), Ministerio de Salud de la Nación, Argentina.
• ³Fundacion INFANT, Buenos Aires, Argentina.
• ⁴Fundacion INFANT, Buenos Aires, Argentina; Vanderbilt University, Nashville, TN, United States; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina.
• ⁵Fundacion INFANT, Buenos Aires, Argentina; Vanderbilt University, Nashville, TN, United States.

Abstract below; full text is available to journal subscribers.

BACKGROUND:

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.

METHODS:

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.

FINDINGS:

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.

INTERPRETATION:

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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