EVALUATION OF MUMPS VACCINE GIVEN AFTER EXPOSURE TO MUMPS, WITH SPECIAL REFERENCE TO THE EXPOSED ADULT

A critical evaluation of inactivated mumps vaccine, given to adults after exposure to mumps, was sponsored by the Maryland Chapter of the American Academy of Pediatrics and was carried out by a member of the Department of Epidemiology of the Johns Hopkins University School of Hygiene and Public Health, selected practicing pediatricians, and the Virology laboratory of the Maryland State Health Department. The study subjects were parents, seen when their children had mumps, who had not themselves had clinical mumps. In a part of the study, selection of subjects for vaccination was by a random method. Among all parents with negative histories, 21/330 or 6.4% had definite clinical mumps. Among 176 vaccinees, 14 had mumps (8%). Among 153 controls 6 had mumps (3.9%). Evaluation of tests for susceptibility indicated that no one with a neutralizing antibody titer of 1-8 or greater came down with mumps. Among controls, all mumps occurred in parents with titers of less than 1-2. Hemagglutination inhibition titers were poorly correlated with immunity, and were not well correlated with neutralizing antibody at low titers. Therefore the HI test is not a reliable method for identifying susceptibles. Although a critical evaluation of the skin test was not made, two vaccinated individuals with positive skin tests came down with mumps. Skin test results did not correlate well with neutralizing antibody titers. Mumps attack rates among exposed parents with negative histories were relatively low, and were lower among fathers than among mothers (5% and 10% respectively). The use of inactivated mumps vaccine in exposed parents is not recommended both for this reason and because of the lack of evidence for any efficacy.