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Measles outbreak in western Sydney: Vaccine failure or failure to vaccinate?
Author(s) -
McDonnell Louise F,
Patel Mahomed S,
Jorm Louisa R
Publication year - 1995
Publication title -
medical journal of australia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.904
H-Index - 131
eISSN - 1326-5377
pISSN - 0025-729X
DOI - 10.5694/j.1326-5377.1995.tb140008.x
Subject(s) - medicine , measles , vaccination , measles vaccine , outbreak , pediatrics , vaccine failure , vaccine efficacy , population , medical record , confidence interval , demography , immunology , environmental health , virology , sociology
Objectives: To determine the effectiveness of measles vaccine during a measles outbreak, and to assess whether age at vaccination was a risk factor for measles vaccine failure. Design: A matched case‐control study. Setting: The five primary schools in western Sydney with the largest number of measles cases during the June to December 1993 outbreak. Subjects: Seventy‐nine children aged 5–9 years with an illness consistent with a clinical definition for measles. Two controls per case were selected from children in the same classroom. Main outcome measures: Estimated measles vaccine effectiveness by age of the child at vaccination and vaccination status: “unvaccinated”; “parental recall” (parents stated the child was vaccinated but no record could be found); and “record” (record including date of vaccination available). Results: The estimated vaccine effectiveness was 94% (95% confidence interval [CI], 83%–98%) in the “record” group, and 81% (95% CI, 46%–93%) in the “parental recall” group. Vaccine effectiveness did not differ significantly with age at vaccination (under 12 months of age 96% [64%–99%]; 12–14 months 95% [81%–99%]; and 15 months and over 93% [80%–98%]). Conclusion: Vaccination records should be used to calculate a vaccine's effectiveness as parental recall may not be sufficiently accurate. The high vaccine effectiveness in the “record” group (94%) makes it unlikely that low vaccine effectiveness was the cause of the outbreak. More effort is needed to increase vaccine coverage to at least 95% in all population subgroups.