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High attack rates and case fatality during a measles outbreak in groups with religious exemption to vaccination
D V Rodgers1, J S Gindler, W L Atkinson
1Division of Immunization, Centers for Disease Control, Atlanta, GA 30333.
Insights
Measles outbreaks disproportionately affected unvaccinated children in Philadelphia. Lack of medical care and pre-existing conditions contributed to a high measles case-fatality rate within religious communities refusing vaccination.
Area of Science:
- Epidemiology
- Public Health
- Infectious Diseases
Background:
- A significant measles outbreak occurred in Philadelphia from October 1990 to June 1991, primarily impacting unvaccinated preschool-aged children.
- Within two specific church groups that decline vaccination, 486 measles cases and 6 associated deaths were documented between November 1990 and March 1991.
- This highlights the vulnerability of unvaccinated populations during widespread infectious disease outbreaks.
Purpose of the Study:
- To investigate the measles outbreak dynamics within unvaccinated religious communities in Philadelphia.
- To identify risk factors associated with measles complications and mortality in this population.
- To analyze the impact of vaccination refusal on disease spread and outcomes.
Main Methods:
- Case identification and data collection on symptoms and potential risk factors for complications.
- Telephone interviews were conducted with measles cases within church member households to gather demographic and clinical information.
- Analysis of age-specific attack rates and case-fatality rates, stratified by gender and disease transmission pathway (primary vs. secondary household cases).
Main Results:
- A total of 486 measles cases were identified among 892 mostly unvaccinated church members.
- Highest age-specific attack rates were observed in children aged 1-4 years (94%) and 5-14 years (91%).
- The overall case-fatality rate was 1.2%, with a higher rate in females (2%) compared to males (0.4%). Five of the six deaths occurred in females, three with underlying illnesses. Only one deceased child had received medical care.
Conclusions:
- Measles spread rapidly through the studied unvaccinated church communities, affecting nearly all susceptible individuals.
- Lack of access to medical care and the presence of underlying health conditions were significant contributing factors to the high case-fatality rate.
- This outbreak underscores the critical importance of vaccination in preventing severe disease and mortality during measles epidemics.
Abstract:
Beginning in October, 1990, a large measles outbreak involving predominantly unvaccinated preschool age children occurred in Philadelphia. By June, 1991, 938 measles cases had been reported to the Philadelphia Health Department. In addition to these cases, 486 cases and 6 measles-associated deaths occurred between November 4, 1990, and March 24, 1991, among members of 2 Philadelphia church groups that do not accept vaccination. We identified measles cases and collected information on symptoms and potential risk factors for complications. Telephone interviews were conducted to collect demographic and clinical information on measles cases in church member households. We identified 486 measles cases among 892 mostly unvaccinated church members. Age-specific attack rates were highest among children 1 to 4 years of age (94%) and 5 to 14 years of age (91%). Five (83%) of the 6 deaths occurred in females, 3 of whom had underlying illnesses. The overall case-fatality rate was 1.2%. The case-fatality rate was 2% for females, 0.4% for males (P = 0.22), 1.7% for primary cases and 0.7% for secondary household cases (P = 0.67). Only one of the children who died had received medical care. Measles spread rapidly in this group, sparing few susceptible individuals. Lack of medical care and underlying disease appear to have contributed to the high case-fatality rate in the church communities.