ABSTRACT

For many years the general belief has been that mumps can be controlled effectively by national vaccine programs against the disease. Chiefly this belief has been founded on the idea that mumps virus represents a monotypic virus like measles and rubella virus. However, in contrast to the situation with measles and rubella virus, several cases of vaccine failures resulting in epidemics have been reported in the literature. In recent years several distinct genotypes of mumps virus based on the nucleotide sequence of the small hydrophobic (SH) protein gene of the virus have been described. In April 2002, 10 different genotypes named A to J have been described. The circulation and co-circulation of virus genotypes in various countries is not possible to predict and it may change with time. A varying degree of neuropathogenic capacity of different virus genotypes has been reported. Important immunological differences between genotypes and even between virus strains within a certain genotype are now in the process of being recognized. These findings may call for a future division of the virus into several distinct virus serotypes. It is concluded that the immunity against mumps is a complicated matter and for accurate estimation it ought to be divided into type-specific immunity against certain virus strains or genotypes. For the future goal of world-wide extinction of the virus it may become necessary to use vaccines based on more than one genotype/serotype of the virus.