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Smallpox epidemic in a Brazilian community.
American Journal of Epidemiology
|June 1, 1975
Summary
The 1969 Utinga, Bahia smallpox outbreak highlights vaccine efficacy at 94%, but shows transmission can persist in unvaccinated pockets. Continued vigilance is crucial even after containment measures.
Area of Science:
- Epidemiology
- Infectious Diseases
- Public Health
Background:
- Brazil experienced a severe smallpox outbreak in Utinga, Bahia in 1969.
- The urban area of Utinga reported 246 smallpox cases out of 507 total cases.
- High susceptibility was observed in unvaccinated children under 15 years old.
Purpose of the Study:
- To detail the smallpox outbreak in Utinga's urban area.
- To assess smallpox vaccine efficacy during the outbreak.
- To understand smallpox transmission dynamics post-containment measures.
Main Methods:
- Case study analysis of the 1969 Utinga smallpox outbreak.
- Vaccine scar assessment for estimating vaccine efficacy.
- Follow-up community visits to monitor transmission.
Main Results:
- Overall attack rate was 11%, with 75% of cases in children under 15.
- Vaccine efficacy was estimated at 94%, with only 4 vaccinated patients.
- Smallpox transmission continued in susceptible pockets despite high community immunity.
Conclusions:
- Smallpox vaccination demonstrates high efficacy (94%) in preventing severe illness.
- Persistent transmission can occur in unvaccinated subgroups, necessitating ongoing surveillance.
- Vaccination during the incubation period may abort clinical illness.