title: Serologic evidence of pertussis infection in vaccinated Iranian children.
abstract: BACKGROUND
  It seems that the incidence of pertussis-like illnesses is considerably increasing despite the wide coverage of immunization with the whole cell pertussis vaccine. We aimed to investigate the occurrence of pertussis in vaccinated children by measuring anti-pertussis antibodies.
  
  
  METHODS
  In this cross-sectional study, blood samples were taken from vaccinated children aged 2, 4, 6, 12, 18, and 72 months. Anti-pertussis IgG and IgA were measured by ELISA. P<0.05 was considered significant.
  
  
  RESULTS
  725 children were enrolled in the study. Geometric mean titers for IgG that showed a slight decease after 2 months of age and increased distinctly in children aged 72 months. The frequency of the individuals whose IgG was above the determined cut-off (derived from mean+2SD) was observed in 1% of the 2, 4, and 6-month-old infants, 6% of the 12 and 18-month-olds and 12% of the 6-year -old children. Positive IgA titers were detected in 5, 9, 6, 23, 11, and 8% of children aged 2, 4, 6, 12, 18, and 72 months, respectively.
  
  
  CONCLUSIONS
  Since a considerable percentage of children had high levels of anti-pertussis IgG antibodies (≥2 SD), positive anti-pertussis IgA, and most importantly an increased level of anti-pertussis IgG geometric mean titer at 6 years of age, further investigations regarding the protection provided by the presently used pertussis vaccine seems necessary.
authors: Department of Pediatric Infectious Diseases, Pediatric Ward, Pediatric Infections Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran;
authors: Anahita Sanaei
authors: AS
authors: Dashti
authors: Abdollah
authors: A
authors: Karimi
authors: Reza
authors: R
authors: Arjmand
authors: Mohsen
authors: M
authors: Moghadami
authors: Taherh
authors: T
authors: Kheirkhah
authors: Farideh
authors: F
authors: Shiva
authors: Zari
authors: Z
authors: Gholinejad
authors: Hassan
authors: H
authors: Joulaei
keywords: Pertussis; Pertussis vaccine; Whooping cough
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