1875. Effectiveness of Tdap Vaccination During Pregnancy in Preventing Infant Pertussis in a Country with Whole-cell Pertussis Vaccines During Childhood: Preliminary Results of a Case-Control Study in Argentina
Session: Poster Abstract Session: Vaccines: Pertussis
Saturday, October 10, 2015
Room: Poster Hall
Background: In 2011, Argentina observed the highest mortality rate from pertussis since 1980; 95% of deaths were among infants <6 months of age. In 2012, vaccination of pregnant women with a dose of diphtheria, tetanus toxoid and acellular pertussis vaccine (Tdap) was recommended at ≥20 weeks gestational age to reduce infant pertussis. At the time of implementation, evidence was lacking on the effectiveness of vaccination during pregnancy in prevention of infant pertussis. 

Methods: We conducted a multi-center,matched case-control evaluation in Argentina to assess the effectiveness of Tdap vaccination during pregnancy in preventing pertussis among infants <2 months of age. Pertussis cases identified at four hospital sites, meeting the suspect case definition, with symptom onset date between September 2012 and March 2014, and confirmed by positive polymerase chain reaction testing were included. Assuming 40% coverage and 60% vaccine effectiveness (VE), target sample size was 69 cases. Five controls were matched to each case by mother’s health district. Maternal vaccination history was collected from vaccination cards, immunization registries or by verbal report. Odds ratios (OR) comparing maternal Tdap receipt between cases and controls were calculated using conditional logistic regression. VE was estimated as (1 - OR) × 100%.

Results: The analysis included 28 cases and 109 controls; target sample size has not yet been met. The percentage of cases and controls whose mothers received Tdap during pregnancy was 43% and 79%, respectively. Preliminarily, maternal Tdap VE was 73.5% (95% confidence interval: 38.4-88.6%).

Conclusion: Argentina was the first country in Latin America to implement routine Tdap vaccination during pregnancy, rapidly reaching 60-65% coverage. To our knowledge, this is the first evaluation of maternal Tdap VE among a population that received whole-cell pertussis vaccines during childhood. Our preliminary analysis shows that vaccination during pregnancy is effective in preventing pertussis in infants <2 months of age. Study enrollment continues in the <2 month age group; additional analyses will include infants up to 12 months of age to determine effectiveness of maternal Tdap in preventing pertussis among older infants.

Viviana Romanin, MD1, Anna M. Acosta, MD2, Sandra Sagradini, MD1, Elizabeth Briere, MD2, Stella Maris Sanchez, MD3, Maria Eugenia Sevilla, MD4, Maria Florencia Lucion, MD5, Anahi Urrutia, Lic6, Maria Del Valle Juarez, MD7, Tami Skoff, MS2 and Carla Vizzotti, MD7, (1)Dinacei, Ministry of Health of Argentina, Buenos Aires, Argentina, (2)Meningitis and Vaccine Preventable Diseases Branch, Centers for Disease Control and Prevention, Atlanta, GA, (3)Hospital del Niņo Jesus, Tucuman, Argentina, (4)"P. de Elizalde" Children Hospital, Buenos Aires, Argentina, (5)Epidemiology, "R. Gutierrez" Children Hospital, Buenos Aires, Argentina, (6)"Dr. H. Heller" Hospital, Neuquen, Argentina, (7)Ministry of Health of Argentina, Buenos Aires, Argentina


V. Romanin, None

A. M. Acosta, None

S. Sagradini, None

E. Briere, None

S. M. Sanchez, None

M. E. Sevilla, None

M. F. Lucion, None

A. Urrutia, None

M. D. V. Juarez, None

T. Skoff, None

C. Vizzotti, None

See more of: Vaccines: Pertussis
See more of: Poster Abstract Session

Findings in the abstracts are embargoed until 12:01 a.m. PDT, Wednesday Oct. 7th with the exception of research findings presented at the IDWeek press conferences.