lets ranged from 5,000 to 90,000 (average, 30,900) in the 12 patients for whom counts were available. In 1934, Perlman reported that there was "a rather constant tendency for the platelet count to drop below normal" (p. 602) in 50 random cases of measles. No data on the degree of thrombocytopenia were provided. Thrombocytopenia has been described as a rare complication of mumps disease (Graham et al., 1974).

Even though large numbers of doses of live attenuated measles vaccine have been administered, very few cases of thrombocytopenia have been reported. In 1965, Katz noted that he was aware of two cases of idiopathic thrombocytopenic purpura and one case of hemolytic-uremic syndrome after approximately 5 million doses of live attenuated measles vaccine had been administered over 6 years. The hemolytic-uremic syndrome is characterized by the triad of hemolytic anemia, thrombocytopenia, and acute renal insufficiency (Kaplan et al., 1987; Levin et al., 1989; Srivastava and Bagga, 1992). Rare cases of this syndrome have been documented following immunization (Srivastava and Bagga, 1992). In addition to the case noted above following administration of live attenuated measles vaccine (Katz, 1965), there have been other cases following administration of mumps vaccine (Dosik and Tricarico, 1970) and MMR (Taranger and Wiholm, 1987).

There are several individual case reports in the literature of thrombocytopenia following administration of live attenuated measles vaccine alone (Alter et al., 1968; Bach and Allard, 1974; DeRitis and Pecorari, 1990; Giroud et al., 1983; Kiefaber, 1981; Medical Journal of Australia, 1980) or concomitantly with immune globulin (Bachand et al., 1967; Saxton, 1967; Wilhelm and Paegle, 1967). Cases of thrombocytopenia also have been reported following administration of measles-mumps vaccine (von Muhlendahl, 1989) and MMR (Azeemuddin, 1987; Neiderud, 1983), but not after administration of mumps vaccine alone (other than that associated with hemolytic-uremic syndrome discussed above). The vast majority of cases of thrombocytopenia occur following the first dose of measles vaccine, but thrombocytopenia has been documented following administration of a second dose as well (Wiersbitzky et al., 1992). It should be noted that comparatively few individuals have received more than one dose of measles vaccine to date.

Case series and uncontrolled observational studies provide the bulk of the information regarding measles and measles-containing vaccines and thrombocytopenia. Taranger and Wiholm (1987) and Bottiger and colleagues (1987) found that 16 cases of thrombocytopenia following administration of MMR were reported to the Swedish health authorities over a 3-year period from 1982 through 1984, when an estimated 700,000 doses of MMR (using