some follow-up beyond 1 year was done to identify residual disorders, the authors did not provide data regarding seizures.

Controlled Observational Studies

The committee was not able to identify any controlled observational studies that reported on the possible association between measles or mumps vaccine and RSD.

Controlled Clinical Trials

As noted above, the Medical Research Council of the United Kingdom reported follow-up data (up to 4 years and 9 months) from a randomized trial of 36,000 patients who received either live attenuated measles vaccine or killed vaccine followed by live attenuated vaccine or no vaccine (Medical Research Council, 1971). Although follow-up was designed to examine the incidence and complications of wild-type measles infection, had an RSD occurred, it might have been noted in such a long-term study. There was no mention of RSD.

Causality Argument

There is evidence that acute seizures are possible sequel of immunization with measles and mumps vaccines. Therefore, it is biologically plausible that there is a connection between immunization and RSD. However, it would be essential to rule out the possibility that the acute cases described in the literature are not febrile seizures, which are common in children and which would not be expected to lead to an RSD. The available data are from case reports and case series; there are no data from observational studies that would allow the calculation of a risk of RSD for vaccinated as opposed to unvaccinated individuals. Perhaps most important, none of the available cases can be confirmed as RSD on the basis of the report alone.

Conclusion

The evidence is inadequate to accept or reject a causal relation between measles vaccine and residual seizure disorder.

There is no evidence bearing on a causal relation between mumps vaccine and residual seizure disorder.

The evidence is inadequate to accept or reject a causal relation between multivalent measles or mumps vaccines and residual seizure disorder.



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