Studies on the Prevention of Mumps

Abstract

Summary Efforts were made to establish suitable dosage schedules for formalin-inactivated mumps virus vaccines. Susceptible children between one and eight years of age were selected on the basis of negative complement fixation (V antigen) and neutralization tests, as well as absence of “booster-type” responses following the first dose of vaccine. These were immunized by the subcutaneous route with 1-ml doses of vaccine at various time intervals. The results were evaluated in terms of anti-V and neutralizing antibody responses and, in one institution, by prevention of illness during an intercurrent outbreak of mumps. A primary course of two doses, one to four weeks apart, following 6–12 months later by a booster dose, gave most satisfactory results. Many of the susceptible children formed some neutralizing antibodies within one to two weeks after the first dose, and nearly all after the second. A third injection at one- to four-week intervals was of little added value. Most of these children failed to reveal detectable antibodies three to six months after the initial dose. A primary course of two or more doses, nevertheless, protected five out of six children against disease during an outbreak of mumps three to eight months later. Subclinical infections were not prevented. The incidence of parotitis in children who had received only one dose corresponded to that in unvaccinated controls. Booster doses 6 or 12 months after the initial course rapidly recalled antibodies and to higher titers than those seen following primary vaccination. Neutralizing antibodies remained detectable in the sera of the majority of the children for 6–12 months thereafter. A second booster after a half year interval did not yield higher titers than elicited by the first. The booster responses in the vaccinated groups failed to match those observed in naturally immunized children following injection of vaccine. The implications of these findings have been discussed.