ANALYSIS OF MUMPS VACCINE FAILURE BY MEANS OF AVIDITY TESTING FOR MUMPS VIRUS-SPECIFIC IMMUNOGLOBULIN-G

To characterize patients with mumps vaccine failure, avidity testing w as performed with the Enzygnost Anti-Parotitis Virus/IgG kit using a s ingle-dilution-6 M urea denaturation method. Five groups of patients w ere tested. Group 1 consisted of 29 patients with primary mumps infect ions; group 2 was 20 children and adults with a definite history of na tural infection; group 3 was 7 patients with a recent mumps vaccinatio n, 1 of whom developed parotid gland swelling and aseptic meningitis; group 4 was 14 patients with mumps vaccine failure; and group 5 was 6 patients with recurrent episodes of parotitis in addition to a history of vaccination. On the basis of the results of groups 1 and 2, an avi dity of less than or equal to 31% was determined to be low, and greate r than or equal to 32% was determined to be high. Avidity maturation f i om low to high appears to occur around 180 days after the acute illn ess. The results of group 3 showed that the vaccine-induced immunoglob ulin G (IgG) had very low avidity. Among the 14 patients in group 4, 1 2 patients, including 7 with a positive IgM response, were diagnosed a s having secondary vaccine failures. The results of group 5 suggested the possibility that the avidity of the mumps vaccine-induced IgG rema ins low or borderline. These results showed that secondary mumps vacci ne failure occurs not infrequently, even among school age children und er condition in which the vaccine coverage is low (i.e., 33% in our st udy population), and therefore, vaccinees are prone to be exposed to w ild-type viruses. Avidity testing should provide information useful fo r the analysis of mumps virus infections.