Adverse events following mumps vaccination
Further to the WHO Position statement on mumps vaccines published in November 2001, the Global Advisory Committee on Vaccine Safety (GACVS) recommended that a comprehensive review of the data on the clinical safety of mumps vaccine strains be conducted to provide a basis for further review of the WHO position regarding the use of different mumps vaccine strains. The review of data was presented to the GACVS at its eighth meeting in Geneva, Switzerland on June 11-12, 2003.
It was noted that higher rates of aseptic meningitis have been described for the Urabe, the Leningrad-Zagreb and the Leningrad-3 strain vaccines compared with the Jeryl-Lynn strain vaccine. The possible virological basis for this difference and/or the other characteristics of the product that might explain these differences are not known. Some of the variability observed in the risk of aseptic meningitis following use of the various mumps vaccine strains may reflect pre-existing immunity, in particular in older age groups, as well as the variable levels of sensitivity of surveillance and of diagnostic practices in different settings. A detailed final report of this review, in which the estimate of risks will be assessed, will be published in due course.
The committee concluded that risk estimates vary between studies, reflecting differences in study settings and circumstances, and degrees of surveillance. The available data are insufficient to distinguish between the safety profile with regard to aseptic meningitis for Urabe, Leningrad-Zagreb and Leningrad-3 strains, respectively. The committee is not aware of any cases of virologically proven aseptic meningitis following Jeryl-Lynn vaccine. If Urabe, Leningrad-Zagreb and Leningrad-3 strain vaccines are being used in mass vaccination campaigns, national immunization programmes need to take into account the potential for clustering of aseptic meningitis following the campaigns. The committee noted that, until now, all reported cases of vaccine-derived mumps meningitis have recovered. There is no known case with long-term sequelae.
The committee further considered a proposal for a mumps vaccine virus strain bank, developed at the invitation of WHO, which has considerable potential scientific interest. Further attention will be given by WHO to the possibility of such a strain bank being established.
The GACVS is a scientific advisory body established by WHO to provide a reliable and independent scientific assessment of vaccine safety issues in order to respond promptly, efficiently and with scientific rigour to such issues. Membership includes experts from around the world in the fields of epidemiology, paediatrics, internal medicine, pharmacology and toxicology, infectious diseases, public health, immunology and autoimmunity, drug regulation, and safety.