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Successful control of a school based measles outbreak by immunization
R A Lyons1, H I Jones, R L Salmon
1PHLS Communicable Disease Surveillance Centre (Welsh Unit), Cardiff.
Epidemiology and Infection
|October 1, 1994
Summary
Rapid vaccination efforts during a 1991 measles outbreak in North Wales successfully reduced susceptible individuals, preventing further spread. The intervention demonstrated high vaccine efficacy, with most cases being preventable.
Area of Science:
- Epidemiology
- Public Health
- Infectious Disease Control
Background:
- A measles outbreak occurred in North Wales in 1991, affecting a secondary school and resulting in 74 cases over 51 days.
- Initially, 27% of pupils were susceptible due to no prior measles history or immunization.
Purpose of the Study:
- To analyze the effectiveness of control measures during a measles outbreak.
- To evaluate vaccine efficacy and identify reasons for outbreak containment.
Main Methods:
- Active case finding and identification of susceptible contacts.
- Vaccination campaign targeting susceptible schoolchildren.
- Analysis of case generations, diagnosis, and notification delays.
- Calculation of observed vaccine efficacy.
Main Results:
- Vaccination efforts reduced the susceptible pool from 17% to 8%, preventing a fifth generation of cases.
- Observed vaccine efficacy was 97%, with no evidence of primary vaccine failure.
- Sixty-nine (93%) of the measles cases were deemed preventable.
Conclusions:
- The intervention, including active case finding and vaccination, was largely successful in controlling the measles outbreak.
- Delays in diagnosis and notification significantly hampered control efforts.
- High vaccine efficacy underscores the importance of timely immunization programs in preventing infectious disease spread.