Infant Pertussis and Household Transmission in Korea

Kwon, Hyo Jin; Yum, Sook Kyung; Choi, Ui Yoon; Lee, Soo Young; Kim, Jong Hyun; Kang, Jin Han

A prospective, multicenter, observational study was conducted between January 2009 and September 2011. Three hospitals participated in the study: Seoul St. Mary's hospital; Suwon St. Vincent's hospital; and Incheon St. Mary's hospital. We evaluated all infants clinically suspected of pertussis infection because of a cough lasting at least 2 weeks with at least one of the following symptoms: paroxysmal coughing; inspiratory whooping; posttussive vomiting or apnea without other known cause. We obtained information on current respiratory manifestations, radiologic findings and immunization status for each infant. Diagnostic approaches for pertussis were conducted for clinical cases. Nasopharyngeal aspirates (NPA), or swab samples if aspirates were not possible, and blood samples were collected within 2 days at admission. Laboratory tests were performed at the Vaccine Bio Institute (VBI) of The Catholic University of Korea. It is determined as the criteria for laboratory-confirmed pertussis case when the subjects is applicable to one of the following criteria: 1) positive result of B. pertussis on culture of nasopharyngeal aspirates (NPA) or swab; this sample was collected and cultured on Regan-Lowe culture medium at 37°C for more than 1 week; 2) positive result of B. pertussis in PCR or real-time PCR (RT-PCR) of NPA or swab; PCR was done by the method Glare et al. reported (16) , and RT-PCR was done by modified method of Reischl U. Colleagues manual (17) ; 3) positive serology which defined as pertussis toxin (PT) antibody in a single serum sample that was higher than cut-off value (24 EU/mL) of enzymelinked immunosorbent assay (ELISA) kit (IBL, Hamburg, Germany) or a 4-fold increased change in anti-PT antibody between acute-phase and convalescent-phase serum.