Epidemiological Characteristics of pertussis Cases Registered at Argentinean National Referente Center During 2003-2006.

GRAIEB AUGUSTO; ROBERTS ROY M; FINGERMANN MATÍAS; BOTTERO DANIELA; SISTI FEDERICO; GAILLARD M.EMILIA; FERNÁNDEZ JULIETA; PIANCIOLA LUIS; LESCANO MIRTA; DIBIASE D,; REGUEIRA MABEL; BINSZTEIN NORMA; RICO OSVALDO; RÍOS GUSTAVO; HOZBOR DANIELA

Baltilmore, USA

Congreso; The Tenth Annual Conference on Vaccine Research. National; 2007

National Foundation for Infectious Diseases.

Background: In many countries pertussis remains endemic, andreemerged despite extensive vaccination. Several explanations wereproposed, mainly regarding problems in the vaccine used. Here weassess the epidemiological situation of pertussis in Argentina, and thepotential contributing factors for its reemergence. Methods: Pertussisdiagnosis was by WHO clinical criteria, laboratory confirmation and/orepidemiological link. Sera and nasopharyngeal samples from 3638patients with clinical signs of pertussis together with epidemiologicaland immunization data were collected during 2003-2006 whenimmunization (whole-cell vaccines) coverage by age two exceed 85%(range 85-90%). Bordetella pertussis isolates obtained in this period werecharacterized by PFGE and prn and ptx genotypes. Comparisons withisolates obtained before 2003 and vaccine strains were included.Results: A total of 1215/3638 cases were confirmed. Most of the caseswere observed in children younger than 6 months; however, high ratesin 1-10 year group were also registered during this period. Noteworthy,238 confirmed cases were registered in 1.5-10 year group with anappropriate vaccination status. This incidence in vaccinated populationseems not due to waning vaccine induced immunity because of patient’sage. PFGE profiles of vaccine strains had only 64 % relatedness with allArgentinean isolates Clinical isolates profiles had a minimum of 80%overall relatedness among them. Moreover, while prn and ptxAsequences from vaccine strains and old isolates contain 1 and 2/4 variantrespectively, new isolates have prn 2 and ptxA 1 alleles. Conclusions:The pertussis cases in well vaccinated patients together with genomicdivergences between clinical isolates and vaccine strains strengthen theneed for evaluating the vaccine formulation