Related Experiment Video
Updated: Sep 21, 2026
Using Reverse Genetics to Manipulate the NSs Gene of the Rift Valley Fever Virus MP-12 Strain to Improve Vaccine Safety and Efficacy
Published on: November 1, 2011
Measles outbreak in 31 schools: risk factors for vaccine failure and evaluation of a selective revaccination strategy
1Department of Preventive Medicine and Biostatistics, University of Toronto, Ont.
Objective:
To examine the risk factors for measles vaccine failure and to evaluate the effectiveness of a selective revaccination strategy during a measles outbreak.
Design:
Matched case-control study.
Setting:
Thirty-one schools in Mississauga, Ont.
Subjects:
Eighty-seven previously vaccinated school-aged children with measles that met the Advisory Committee on Epidemiology's clinical case definition for measles. Two previously vaccinated control subjects were randomly selected for each case subject from the same homeroom class.
Interventions:
All susceptible contacts were vaccinated, and contacts who had been vaccinated before Jan. 1, 1980, were revaccinated. When two or more cases occurred in a school all children vaccinated before 1980 were revaccinated.
Main Outcome Measures:
Risk of measles associated with age at vaccination, time since vaccination, vaccination before 1980 and revaccination.
Results:
Subjects vaccinated before 12 months of age were at greater risk of measles than those vaccinated later (adjusted odds ratio [OR] 7.7, 95% confidence interval [CI] 1.6 to 38.3; p = 0.01). Those vaccinated between 12 and 14 months of age were at no greater risk than those vaccinated at 15 months or over. Subjects vaccinated before 1980 were at greater risk than those vaccinated after 1980 (adjusted OR 14.5, 95% CI 1.5 to 135.6). Time since vaccination was not a risk factor. Revaccination was effective in reducing the risk of measles in both subjects vaccinated before 1980 and those vaccinated after 1980 (adjusted OR reduced to 0.6 [95% CI 0.1 to 5.3] and 0.3 [95% CI 0.13 to 2.6] respectively). However, only 18 cases were estimated to have been prevented by this strategy.
Conclusions:
Adherence to routine measles vaccination for all eligible children is important in ensuring appropriate coverage with a single dose. The selective revaccination strategy's high labour intensiveness and low measles prevention rate during the outbreak bring into question the effectiveness of such a strategy.
Insights
Measles vaccine failure is linked to early vaccination. A selective revaccination strategy during an outbreak was labor-intensive and prevented few cases, questioning its overall effectiveness.
Area of Science:
- Epidemiology
- Vaccinology
- Public Health
Background:
- Measles vaccine failure can occur, necessitating an understanding of risk factors.
- Outbreaks highlight the need for effective vaccination and revaccination strategies.
Purpose of the Study:
- To identify risk factors associated with measles vaccine failure.
- To assess the efficacy of a targeted revaccination approach during a measles outbreak.
Main Methods:
- A matched case-control study was conducted in 31 schools.
- Eighty-seven vaccinated children with measles (cases) were compared to 174 vaccinated controls.
- Interventions included vaccinating susceptible contacts and revaccinating those vaccinated before 1980.
Main Results:
- Vaccination before 12 months of age significantly increased measles risk (adjusted OR 7.7).
- Vaccination before 1980 also posed a higher risk (adjusted OR 14.5).
- Revaccination showed potential benefit but prevented an estimated 18 cases, indicating limited impact.
Conclusions:
- Routine measles vaccination adherence is crucial for single-dose coverage.
- The selective revaccination strategy was labor-intensive with a low prevention rate, raising doubts about its outbreak effectiveness.
Related Concept Videos
01:51Vaccinations
01:28Infectious Diseases and Their Occurrence
01:21Vaccines
01:24Smallpox
01:17Poliomyelitis
01:29Respiratory Syncytial Virus Disease