Sir.—Dr Pachman,1 in the May issue of AJDC, suggests that adolescents should receive a booster dose of mumps vaccine based on "a high incidence in the 10- to 20-year-old group, many of whom had been previously vaccinated in early childhood".
Dr Pachman does not tell us whether or not any of these cases of "mumps" were confirmed by acute and convalescent serologic studies. It is well known that other paramyxoviruses can produce a clinical picture that is indistinguishable from mumps. This fact and the problem of serologic confirmation of mumps were both addressed in the article by Cochi et al2 in the same issue.
As the incidence of parotitis due to mumps declines because of immunization, a greater proportion of parotid gland swellings will be attributed to the other viruses. I suggest that the epidemic of mumps that Dr Pachman reports may have been due to one of