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[Mumps epidemic in vaccinated children in West Switzerland]
A Ströhle1, K Eggenberger, C A Steiner
1Institut fr Medizinische Mikrobiologie, Universität Bern.
Insights
Low measles, mumps, and rubella (MMR) vaccine coverage and issues with the Rubini vaccine strain contributed to widespread mumps outbreaks in Switzerland. This highlights the need for higher vaccination rates and potentially improved vaccine efficacy.
Area of Science:
- Virology
- Immunology
- Epidemiology
Context:
- Switzerland experienced significant mumps outbreaks from 1991 onwards, despite universal measles, mumps, and rubella (MMR) vaccination recommendations.
- A high proportion of mumps cases (up to 80%) occurred in previously vaccinated children, primarily those who received the Rubini vaccine strain.
Purpose:
- To investigate the complex factors contributing to large-scale mumps vaccine failure in Switzerland.
- To analyze the efficacy of the Rubini vaccine strain and identify reasons for its widespread failure.
Summary:
- The study identified four key factors: insufficient national vaccine coverage (around 80% instead of the required 90-95%), frequent primary and secondary vaccine failures associated with the Rubini strain, genetic divergence of the Rubini strain from circulating wild mumps viruses, and structural differences in the hemagglutinin neuraminidase protein affecting neutralization.
Impact:
- Findings underscore the critical need for achieving higher MMR vaccination coverage to prevent mumps outbreaks.
- The study suggests potential issues with the Rubini vaccine strain's immunogenicity and strain-specific protection, necessitating further research into vaccine composition and effectiveness.
Abstract:
Since 1991, 6 years after the recommendation of universal childhood vaccination against measles, mumps, and rubella (MMR triple vaccine), Switzerland is confronted with a large number of mumps cases affecting both vaccinated and unvaccinated children. Up to 80% of the children suffering from mumps between 1991 and 1995 had previously been vaccinated, the majority with the Rubini vaccine strain. On the basis of a case-control study including 102 patients and 92 controls from the same pediatric population, a study of the humoral immune-response following vaccination with the Rubini vaccine in 6 young adult volunteers, and two different genetic studies, we investigated the complex problem of large scale vaccine failure in Switzerland. We conclude that the recently reported large number of Swiss mumps cases was caused by at least four interacting factors: 1. A vaccine coverage of 90-95% at the age of 2 years is necessary to interrupt mumps wild virus circulation. The nationwide vaccine coverage in Switzerland of some 80% in 27-36 month-old children is too low. 2. Primary vaccine failures (absence of seroconversion or unprotective low levels of neutralizing antibodies), as well as secondary vaccine failures due to the rapid decline of antibodies to mumps virus in our volunteers and controls, seem to be frequent after vaccination with the Rubini strain. 3. Despite its reported Swiss origin, the Rubini strain does not belong to the mumps virus lineages recently circulating in this area but is closely related to American mumps virus strains. 4. Differences in protein structure between the vaccine strain and the circulating wild type strains, and in particular a different neutralization epitope in the hemagglutinin neuraminidase protein, may additionally contribute to the lack of protection in vaccinated individuals.