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Epidemiology of pertussis, Atlanta, 1977
Insights
Pertussis vaccination is 63% effective, with higher attack rates in unvaccinated infants. Asymptomatic cases were more likely to have received multiple vaccinations.
Area of Science:
- Epidemiology
- Immunology
- Public Health
Background:
- Pertussis outbreaks pose a significant public health risk, particularly to vulnerable populations.
- Understanding transmission dynamics and vaccine effectiveness is crucial for controlling pertussis (whooping cough).
Purpose of the Study:
- To investigate the epidemiology of a pertussis outbreak.
- To determine vaccine efficacy and identify risk factors for infection.
Main Methods:
- Retrospective study of 115 pertussis cases diagnosed via culture or direct fluorescent antibody (FA) testing.
- Analysis of secondary household attack rates stratified by age.
- Estimation of vaccine efficacy and identification of asymptomatic carriers.
Main Results:
- Secondary attack rates were highest in infants (81%) and decreased with age.
- Overall pertussis vaccine efficacy was estimated at 63%.
- Asymptomatic individuals were more likely to have received multiple vaccinations compared to symptomatic children.
Conclusions:
- Pertussis vaccination demonstrates significant efficacy in preventing disease.
- Infants are at the highest risk during outbreaks.
- Further investigation into vaccination status of asymptomatic carriers is warranted.
Abstract:
In the period April to October, 1977, an epidemic of pertussis in the outpatient population of a large metropolitan hospital involved 115 cases that were diagnosed by culture or direct fluorescent antibody tests. A study of secondary cases in household contacts showed attack rates of 81% in children under one year of age; attack rates decreased with increasing age to 8% in persons over 20 years of age. Vaccine efficacy was estimated to be 63%. There was no evidence of decreased efficacy with increasing time after vaccination. Fourteen asymptomatic FA-positive individuals were identified; four of these were also culture positive. Four were adults and ten were children. Nine of the ten children had received three or more vaccinations, compared to only 29 of 78 symptomatic children (P = 0.002).