Measles, Mumps, and Rubella - Centers for Disease Control and ...

28 MMWR May 22, 199840,000 in Sweden (169 ), with a temporal clustering of cases occurring 2–3 weeks aftervaccination. Based on passive surveillance, the reported frequency of thrombocytopeniawas approximately 1 case per 100,000 vaccine doses distributed in Canada(170 ) and France (171 ), and approximately 1 case per 1 million doses distributed inthe United States (172 ). The clinical course of these cases was usually transient andbenign, although hemorrhage occurred rarely (172 ). The risk for thrombocytopeniaduring rubella or measles infection is much greater than the risk after vaccination(173 ). Based on case reports, the risk for MMR-associated thrombocytopenia may beincreased for persons who have previously had immune thrombocytopenic purpura,particularly for those who had thrombocytopenic purpura after an earlier dose ofMMR vaccine (150,174,175 ).Neurological EventsAdverse neurological events after administration of MMR vaccine are rare. Reportsof nervous system illness following MMR vaccination do not necessarily denotean etiologic relationship between the illness and the vaccine. Although several casesof sensorineural deafness have been reported after administration of MMR vaccine,evidence from these case reports (e.g., timing of onset and other features) is inadequateto accept or reject a causal relation between MMR vaccination and sensorineuraldeafness.Aseptic MeningitisAseptic meningitis has been clearly associated with administration of the Urabestrain mumps vaccine virus but not with the Jeryl Lynn strain, which is the onlymumps vaccine used in the United States (176–178 ). Sentinel surveillance laboratoriesin the United Kingdom identified thirteen aseptic meningitis cases (91 cases per1 million doses distributed) that occurred after administration of the Urabe strain vaccineduring 1988–1992 (168 ). Since the United Kingdom switched to Jeryl Lynn strainvaccine in 1992, no mumps vaccine-associated aseptic meningitis cases have beenreported by the surveillance laboratories (178 ).Subacute Sclerosing Panencephalitis (SSPE)Measles vaccination substantially reduces the occurrence of SSPE as evidenced bythe near elimination of SSPE cases after widespread measles vaccination. SSPE hasbeen reported rarely among children who had no history of natural measles infection,but who had received measles vaccine. Evidence indicates that at least some of thesechildren had unrecognized measles infection before they were vaccinated and that theSSPE was directly related to the natural measles infection. The administration of livemeasles vaccine does not increase the risk for SSPE, even among persons who havepreviously had measles disease or received live measles vaccine (150,179 ).Encephalopathy/EncephalitisEncephalitis with resultant residual permanent central nervous system (CNS) impairment(encephalopathy) develops in approximately 1 per 1,000 persons infectedwith measles virus. Whether attenuated live viral measles vaccine can also producesuch a syndrome has been a concern since the earliest days of measles vaccine use.