Neutralizing and hemagglutination-inhibiting antibodies to rubella virus as indicators of protective immunity in vaccinees and naturally immune individuals.

In general, hemagglutination-inhibiting (HAI) and neutralizing (NT) antibodies to rubella virus tend to parallel one another, and the presence of either antibody has been interpreted as reflecting protective immunity. It has recently been shown that persons who have HAI antibody but lack NT antibody may be subject to reinfection. In the present study these two antibodies were compared with regard to their appearance and persistence in vaccines and in those who have experienced natural infection. NT antibody appeared more slowly following immunization with HPV77DE5 or Cendehill vaccines than after natural infection or immunization with RA 27/3 vaccine. As with natural infection, initial NT antibody responses to RA 27/3 vaccine were of higher titer and persisted at higher levels for three years than was the case with either of the other vaccines. NT testing procedures were found to differ in sensitivity, depending on several factors including the cells in which the virus was grown.