Responses of previously reinfected rubella vaccinees to challenge with Brown strain rubella virus.

The responses of seven hpv-77 rubella vaccinees to initial challenge with "wild" rubella virus have been compared with their responses to rechallenge with Brown strain rubella virus and to the responses of five "natural" immunes to initial Brown strain challenge. Previous exposure to "wild" rubella virus 220 days post vaccine-induced immunity had resulted in six of the seven vaccinees experiencing asymptomatic reinfection. On "rechallenge" none of the previously "reinfected vaccine immunes" demonstrated clinical, virologic or serologic evidence of reinfection. These data are consistent with the conclusion that persons with vaccine-induced immunity may be assured of more prolonged and solid immunity to rubella without having to suffer the clinical disease if they are reinfected with nonattenuated rubella virus. Rigidly controlled experiments, designed to study the practicality and safety of immunization with live rubella vaccine(s), followed by deliberate challenge of vaccinees with "wild" or low tissue culture passage rubella virus, seem warranted. In addition, these data indicate that it is imperative that a distinction should be made between "vaccine immunes" and previously "reinfected vaccine immunes" in any evaluation of long term rubella vaccine(s) efficacy and vaccine-induced antibody decay.