Introduction: Pertussis or whooping cough is one of the vaccine preventable diseases. The purpose of this study was to
evaluate the seroepidemiology of pertussis in two groups of children (i.e. under 2 months and 2-12 months old) who
had been admitted to Tehran Children Hospital. Methods: Sampling from the children was done along with completing
a questionnaire including demographic information, clinical symptoms and the history of the parents coughing. The
levels of IgG-Ptx antibody were then measured using the children's sera. Results: Overall, 10.8% of the children were
not immune, 78.3% were immune, and 10.9% had recent pertussis infections. Moreover, 19.4% of the female and
13.1% of the male subjects had the infection. In the age group less than two months, 16.6% were infected. The
likelihood of new infection among the children less than 2 months old was 1.2 times higher than the control group (P <
0.004). Fifty percent of the children who were diagnosed with cyanosis in their clinical examinations had a recent
infection (P <0.001).  Conclusion: Pertussis appears to be endemic in Iran with children under one year old being at
high risk of the infection. In this regard, maternal vaccination against pertussis for conferring passive immunity to the
newborns could be considered as a protection measure.