Pertussis epidemiology in Argentina over 2006-2008: trends by age group and status of vaccination

FLORES, D; WELTMAN, GABRIELA; ZURITA, E; LARA, C; FIORITI, A; ARCHUBY, D; BOTTERO, DANIELA; BARBERO, P; BETTIOL, M; GATTI, BLANCA; GRAIEB, AUGUSTO; GAILLARD, MARIA EMILIA; FINGERMANN, MATÍAS; SISTI, FEDERICO; FERNANDEZ, JULIETA; CASTUMA C; GONZALEZ AYALA SE; GALAS, M; HOZBOR, DANIELA

Bruselas, Bélgica

Congreso; 27th Annual Meeting of the European Society for Paediatric Infectious Disease; 2009

European Society for Paediatric Infectious Disease

Background and aims: Pertussis is a vaccine-preventable disease caused by Bordetella pertussis. Despite good vaccination coverage in Argentina, disease incidence increased 6-fold since 2002. Here we describe pertussis epidemiology in Argentina during 2006-2008 and discuss possible reasons for increase.Methods: CDC criteria were used for pertussis diagnosis. Proportion of pertussis cases by age, immunization status, and immunization coverage rate evaluated at the Argentinean National Pertussis Reference Center are reported. B. pertussis isolates were characterized by pulse filed gel electrophoresis (PFGE) and prn and ptx genotypes. Comparisons with vaccine strains are included.Results: From 8,176 patients with pertussis clinical signs, 22.9% were confirmed: 523 in 2006, 617 in 2007, and 734 in 2008. Approximately 55% occurred at Buenos Aires and Córdoba, the most populated regions. Though a clear increase is observed at all age groups compared to previous data, children <6 months old had the highest proportion of cases. In this age group a delay in vaccine application was registered, 30% of infants had fewer vaccine doses than they should. In addition, molecular characterization of the isolates revealed a genotypic divergence between them and the vaccine strains. PFGE profiles of vaccine strains had only 64% relatedness with all Argentinean isolates analyzed. Moreover, while vaccine strains contain prn1/7 and ptxS1 B/D alleles, local isolates have prn2 and ptxS1A.Conclusions: Pertussis is an important problem for public health in Argentina. Delay in vaccine application, and divergence between vaccine strains and local isolates could contribute to the described pertussis epidemiology.