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Outbreak of pertussis in highly immunized adolescents and its secondary spread to their families
T Aoyama1, M Harashima, K Nishimura
1Department of Pediatrics, Kawasaki Municipal Hospital, Japan.
Insights
Pertussis outbreaks can occur in highly vaccinated populations. Vaccine immunity wanes 6-10 years post-vaccination, necessitating updated DTP booster immunizations for pertussis control.
Area of Science:
- Pediatric infectious diseases
- Immunology
- Vaccinology
Background:
- Pertussis (whooping cough) remains a public health concern.
- Vaccine-induced immunity duration is critical for sustained protection.
Purpose of the Study:
- To investigate a pertussis outbreak in a vaccinated school population.
- To assess the effectiveness of DTP vaccination over time.
Main Methods:
- Studied a sixth-grade class with a high immunization rate.
- Identified pertussis cases and calculated attack rates.
- Assessed secondary household transmission.
Main Results:
- Eight pertussis cases occurred, seven in fully DTP-immunized children (18.4% attack rate).
- Immunity waned significantly 6-10 years after the last DTP dose.
- Secondary household spread was observed.
Conclusions:
- Pertussis vaccine effectiveness decreases significantly over time.
- Booster immunizations with DTP are recommended over DT for pertussis control.
Abstract:
An outbreak of pertussis was recognized in a highly immunized sixth-grade class of schoolchildren. Among 43 children aged 11-12 years in the class, 38 had been immunized with three doses or more of DTP containing whole-cell pertussis vaccine, two with two doses of DTP and three children were unimmunized. The last DTP vaccines had been given 6-10 years before the outbreak. A total of eight children with pertussis suffering paroxysmal coughing attacks for 3 weeks or more were identified, seven being fully immunized and one unimmunized. Among the eight cases, two were confirmed by both culture and serology and one by serology alone. The attack rate in fully immunized children was 18.4% (7/38). Secondary spread of pertussis was identified in five of the households from which the eight patients originated. A total of six cases of pertussis from these five households were identified, and two of these were culture-confirmed. These observations suggest that vaccine-induced immunity weakens considerably 6-10 years after vaccination, and that booster immunization with DTP instead of DT is therefore recommended for the control of pertussis.