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Measles elimination: old and new challenges?
1Department of Immunology, WHO Collaborative Center for Measles, Laboratoire National de Santé, P.O. Box 1102, L-1011, Luxembourg. claude.muller@santel.lu
Abstract:
Life attenuated measles vaccines have dramatically reduced measles morbidity and mortality world-wide. Despite high vaccination coverage, measles outbreaks continue to occur both in developed and developing countries. While secondary vaccine failure may be responsible for disease in some seroconverted individuals, evidence suggests that many more vaccinees who are protected against disease may not be fully protected against virus infection. In low-income developing countries protection by maternal antibodies seems to erode faster than previously estimated especially in infants who were born to vaccinated mothers. Problems of infectivity and susceptibility of vaccinees will be compounded in case wild-type viruses become less sensitive to vaccine induced immunity. These observations suggest that elimination may be more easily achieved as long as large proportions of populations are protected by wild-type virus-induced immunity.
Insights
Measles vaccines reduce illness and death, but outbreaks persist. Some vaccinated individuals may not be fully protected against measles virus infection, impacting elimination efforts.
Area of Science:
- Immunology
- Vaccinology
- Public Health
Background:
- Measles vaccines have significantly decreased global measles morbidity and mortality.
- Despite high vaccination rates, measles outbreaks persist worldwide, indicating challenges in disease control.
Purpose of the Study:
- To investigate the reasons behind ongoing measles outbreaks despite widespread vaccination.
- To assess the extent of protection against measles virus infection versus disease in vaccinees.
Main Methods:
- Review of existing literature on measles vaccine efficacy and post-vaccination immunity.
- Analysis of factors contributing to measles outbreaks in various settings.
- Examination of the role of maternal antibodies and potential waning immunity in infants.
Main Results:
- Evidence suggests that many vaccinated individuals are protected against disease but not fully against measles virus infection.
- Maternal antibody protection appears to wane faster than previously thought, particularly in infants born to vaccinated mothers.
- Potential reduced sensitivity of wild-type viruses to vaccine-induced immunity could exacerbate susceptibility.
Conclusions:
- Achieving measles elimination may be more feasible with substantial population immunity derived from wild-type virus exposure.
- Further research is needed to understand and address the nuances of vaccine-induced immunity and susceptibility to measles infection.