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Secondary failure rates of measles vaccines: a metaanalysis of published studies
J F Anders1, R M Jacobson, G A Poland
1Mayo Medical School, Rochester, MN, USA.
Background:
Recent measles outbreaks in highly vaccinated populations have highlighted the role of vaccine failure as a barrier to the elimination of measles. We sought to estimate the rate of secondary failure (clinical measles after vaccine-induced seroconversion) of measles vaccines using metaanalysis.
Methods:
We identified 1411 studies of which 125 were relevant. From these we found 10 original studies of healthy subjects with sufficient details to calculate a pooled secondary failure rate. We performed a test for homogeneity before any pooling.
Results:
Although significant heterogeneity prevented their pooling as a single group, the studies fell into three homogeneous groups suitable for pooling. Group A studies used killed vaccine whereas the other two groups (Groups B and C) of studies used live vaccine. These latter groups differ in that the studies in Group B share higher failure rates and are difficult to interpret with respect to the lack of verification of vaccination, immunization before 12 months of age and a non-North American study site and vaccine manufacturer. Those studies in Group C, in which US subjects were older than 12 months at vaccination and received a live US-manufactured vaccine that was documented in a medical record, had a failure rate of 0 of 2031 with a 95% confidence interval of 0.0 to 0.147%.
Conclusions:
Although reports of measles related to secondary failure exist, studies that permit the calculation of the rate of secondary failure demonstrate that the rate appears to be < 0.2%.
Insights
Measles vaccine failure is a concern in outbreaks. A meta-analysis found the secondary failure rate, clinical measles after vaccination, is less than 0.2% in well-documented cases.
Area of Science:
- Immunology
- Epidemiology
- Vaccinology
Background:
- Measles outbreaks in vaccinated populations indicate vaccine failure is a barrier to disease elimination.
- Secondary vaccine failure, clinical measles post-seroconversion, is a key factor in measles persistence.
Purpose of the Study:
- To estimate the rate of secondary failure for measles vaccines using a meta-analysis approach.
- To identify factors influencing measles vaccine efficacy and failure rates.
Main Methods:
- A meta-analysis was conducted on 10 original studies of healthy subjects with sufficient data.
- Studies were screened from 1411 identified articles, with homogeneity tests performed before pooling data.
Main Results:
- Significant heterogeneity was observed, leading to the formation of three distinct study groups.
- Studies using live vaccines in US subjects, vaccinated after 12 months with documented records (Group C), showed a secondary failure rate of 0% (95% CI: 0.0-0.147%).
- Killed vaccines (Group A) and live vaccines with less robust data (Group B) exhibited higher, unpooled failure rates.
Conclusions:
- The secondary failure rate of measles vaccines appears to be less than 0.2% in rigorously studied populations.
- While secondary failure contributes to measles cases, optimal vaccination practices significantly minimize this risk.