Development of immunoglobulin M-antibodies after rubella immunization with RA27/3 attenuated live vaccine in teen-agers: remaining problems.

Four-hundred-fourty-two rubella seronegative teen-agers living in Siena and the surroundings were vaccinated with RA 27/3 live attenuated rubella over a two years period (1985-1987). One-hundred-twenty seven vaccinees' sera were randomly selected for the rubella specific antibodies of the IgM class detection with two Elisa Methods; the sera were collected 10 and 30 days after the challenge; in 58 girls a serum sample was also obtained 1 yr later. None of the sera showed reactivity for RF. The comparison between the two Elisa methods gave satisfactory results, the percentage of discrepancies being low (3.9%). Ten days after the immunization the IgM positive sera were only 7.56% (Elisa Abbott) and 5.88% (Elisa Enzygnost Behringwerke). One month later, 86.61% of the specimens showed reactivity for specific IgM antibodies. None of 58 sera gave positive results after 1 yr. Rubella antibodies of the IgG class could be demonstrated in the "screening" sera of 3 IgM negative subjects, when an Elisa method was applied. Nine subjects (7%) repeatedly resulted IgM negative one month after the challenge although a seroconversion was observed using both HAI and EIA. A serum sample was also obtained in 6/9 IgM "non responders" after a rubella epidemic observed in 1988-1989; no subclinical reinfection due to the wild virus was detected in this group, no changes in HAI antibody title nor evidence of IgM class specific response were observed. Although most of the diagnostic aspects related with rubella and rubella vaccination appear to be resolved, it should be underlined that there are several remaining problems especially associated with IgM detection.