Commentary: Ongoing debate over the safety of the different mumps vaccine strains impacts mumps disease control.

Abstract

The worldwide use of vaccines has resulted not only in significant achievements in controlling disease but also in disease eradication; smallpox was eradicated in 1977 and there is a global goal for polio eradication by 2005. Additionally, global efforts are already underway towards accelerated measles control. In 1992, mumps disease was recognized as one of six potentially eradicable diseases by the International Task Force for Disease Eradication (ITFDE). 1 The ITFDE is a group of scientists convened through the Carter Center of Emory University in Atlanta, GA, that met from 1989 to 1992 to evaluate the potential for eradication of more than 90 diseases. The ITFDE also recognized the potential for the eradication of rubella and suggested that the effort to eradicate measles, mumps and rubella be combined through the use of the trivalent MMR (measles-mumps-rubella) vaccine. Today, as many countries embark on accelerated measles control or elimination activities, there is a unique opportunity to control mumps and rubella diseases and to work towards the ITFDE goal of eradication through use of the MMR vaccine. However, this opportunity is being missed while debate continues concerning the safety profiles of the different mumps vaccine strains to be incorporated in MMR formulations. Opportunities for control are also affected by differences in the cost of vaccines prepared with the different strains. The present paper 2 adds to the debate by contributing additional data on the safety profile of the Leningrad Zagreb strain of the mumps vaccine and discussing the issues of cost as they relate to national immunization programmes. Both safety and cost have implications for the global use of mumps-containing vaccines and the control of mumps disease worldwide. The most frequent serious complication following wild mumps infection is aseptic meningitis. 3 Wild virus mumps infection leads to aseptic meningitis in up to 10% of patients. The attenuated vaccine-strain virus poses a much lower risk of aseptic meningitis following vaccination, however the risk varies from strain to strain. Estimates ranging from 1 case in 150 000 doses of vaccine administered for the Jeryl Lynn strain, developed in the US, 4 to 1 case in 1000 for the Leningrad-3 strain, developed in Russia, have been found. 5 In the early 1990s, use of the Urabe strain of mumps vaccine virus, developed in Japan, was discontinued in many countries (Japan, Canada and the UK) due to the occurrence of aseptic meningitis following vaccination. 6 It is important to note that cases of aseptic meningitis following vaccination resolve completely and without sequelae. The Rubini strain of mumps vaccine virus, developed in Switzerland, is a strain about which there is no debate concerning its use; the use of vaccines made with this strain are not recommended by WHO for use in national programmes due to their low effectiveness. This risk of aseptic meningitis following vaccination has caused some countries to elect not to use the MMR vaccine made with either the Urabe strain or one of the two Leningrad series of strains (the Leningrad-3 vaccine virus was further attenuated to the Leningrad-Zagreb strain, which was developed in Croatia) for mass vaccination campaigns. These countries have elected to use either the bivalent measles-rubella vaccine or the monovalent measles vaccine rather than use the more expensive Jeryl Lynn MMR vaccine. An opportunity to control mumps disease is thus lost.