Circulation of Bordetella pertussis in vaccinated Cambodian children: A transversal serological study

Abstract

Background: The Cambodia pertussis immunization schedule includes three doses given at age 6, 10 and 14 weeks using a whole-pertussis vaccine. No booster doses are included. Pertussis biological diagnosis is unavailable in Cambodia and its burden remains unclear. This study aimed to provide accurate data on pertussis serological status of Cambodian children and adolescents, and to evaluate vaccination timeliness.

Methods: Fully vaccinated children aged 3-15 years were recruited at the Rabies Prevention Center, Institut Pasteur in Cambodia, Phnom Penh. Capillary blood samples and information on pertussis vaccination history were collected. Anti-pertussis toxin (PT) IgG titers were quantified by ELISA.

Results: Compliance with the national immunization schedule was 95.1%. Initiation of vaccination after 8 weeks of age was observed for 29.0% of the children, but was less frequent in the youngest children (13.0%) compared with the oldest ones (46.4%). Rate of children exhibiting anti-PT IgG varied across age groups, and increased from 35.7% to 55.0% in 3-5 and 12-15 years age groups, respectively.

Conclusion: Pertussis circulates among vaccinated Cambodian children and adolescents. These data support the need for public health authorities to strengthen pertussis surveillance and use local epidemiological data to make evidence-based decision for the establishment of an optimal vaccination strategy.

Keywords: Cambodia; Pertussis; Sero-prevalence; Timeliness; Whole-cell vaccine.