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Serologic evidence of subclinical pertussis in immunized children
S S Long1, H W Lischner, A Deforest
1Department of Pediatrics, St. Christopher's Hospital for Children, Philadelphia, PA 19134.
Insights
Inner city children showed higher pertussis antibody levels than suburban children, indicating increased natural Bordetella infection risk. Proximity to reported pertussis cases correlated with these elevated antibody titers.
Area of Science:
- Immunology
- Pediatrics
- Public Health
Background:
- Pertussis (whooping cough) remains a concern despite vaccination.
- Socioeconomic factors may influence vaccine effectiveness and natural infection rates.
- Assessing natural Bordetella pertussis infection is crucial for understanding disease transmission.
Purpose of the Study:
- To compare pertussis antibody titers between inner city and suburban children.
- To investigate the prevalence of natural Bordetella pertussis infection in different urban settings.
- To correlate antibody levels and infection evidence with geographic proximity to pertussis cases.
Main Methods:
- Analysis of pertussis antibody titers (agglutinin, antitoxin, IgG, IgA) in 783 immunized children.
- Serological testing for natural infection in 332 children from a placebo arm.
- Correlation of antibody rises with residential location and reported pertussis cases.
Main Results:
- Inner city children had significantly higher pertussis agglutinin titers before the fourth vaccine dose.
- 11% of inner city children versus 1.3% of suburban children showed serologic evidence of natural infection.
- Serologic evidence of infection in inner city children was linked to proximity to reported pertussis cases.
Conclusions:
- Inner city children may have a higher risk of natural pertussis exposure and infection.
- Geographic clustering of pertussis cases influences infection risk in unvaccinated children.
- Environmental and socioeconomic factors warrant consideration in pertussis control strategies.
Abstract:
Incidental to a vaccine study involving 783 immunized children conducted at two study sites, inner city children had significantly higher geometric mean pertussis agglutinin titers compared with suburban children just before the fourth dose of diphtheria-tetanus-whole cell pertussis vaccine (47 vs. 25; P less than 0.001). Higher titers in the inner city were correlated with residence in census tracts where cases of pertussis were reported. Three hundred thirty-two children in a placebo arm of the study who were clinically observed and had paired serum samples taken during a 2- to 4-month period were analyzed for evidence of natural Bordetella infection. Twelve (11%) inner city children and three (1.3%) suburban children had spontaneous 4-fold or greater rises in at least two different pertussis antibodies measured (agglutinin, antitoxin or enzyme-linked immunosorbent assay for IgG to pertussis toxin, IgG and IgA to filamentous hemagglutinin). Eighty percent of these children had IgA to filamentous hemagglutinin. Nine of 12 inner city children with serologic evidence of pertussis lived within 6 blocks of a case of pertussis reported within 1 month of the observed antibody rise in study subjects; none had a household member with pertussis and none had symptomatic disease.