Cell-mediated immune response following natural rubella and rubella vaccination.

Cell-mediated immunity (CMI), determined by estimating the production of MIF from sensitized leucocytes, was followed for 12 months after natural rubella infection (twenty-two subjects) and after vaccination with the Cendehill strain of attenuated rubella virus vaccine (forty subjects). Results were compared and correlated with the development of rubella haemagglutination inhibition antibody. The cell-mediated immune response commenced 1 week before the humoral immune response, but both responses reached a maximum simultaneously whether induced by natural infection or by vaccination. However, the CMI following natural rubella infection was of greater magnitude and duration than that stimulated by the vaccine virus. Twelve months after the initial stimulus, CMI could not be detected in any of the vaccinees, but was still present in some individuals after natural infection. This ability of the Cendehill vaccine virus to stimulate only shortlived, detectable CMI may be an important factor in the high reinfection rate observed following rubella vaccination.