Transmission of rubella vaccine virus from vaccinees to contacts.

The report presents evidence of the transmission of hpv-77 derived rubella vaccine virus from vaccinees to two susceptible contacts. The first instance of transmission was to a child who served as a transmission control on a "closed" study ward, and the second was to an antibody-negative mother in an "open" family study. Neither of these persons had any clinical evidence of rubella. Both had significant increases in rubella hemagglutination inhibiting (hai) antibody titers, but detectable complement fixing (cf) antibodies did not develop in either. With the kind of antigen used in our rubella cf test, this pattern of serologic response is characteristic of, but not diagnostic of, infection with the rubella vaccine virus. The serological evidence which was compatible with rubella vaccine virus infection, the complete absence of serologic or clinical evidence of "wild" rubella virus infections among the other four rubella susceptible transmission control children and the security precautions employed to ensure isolation on the "closed" ward, make "wild" rubella virus infection extremely unlikely. The evidence for rubella vaccine virus infection in the other susceptible contact is not as conclusive, because "wild" rubella virus infection is difficult to rule out in any person living in an "open" family situation. Nevertheless the need for more data is emphasized by the virtual certainty that rubella vaccine virus transmission did occur in the subject on the isolation ward, plus the high probability that the infection observed in the family group setting also represented transmission of rubella vaccine virus. Such data can only come from close surveillance of recipients of live rubella virus vaccines and their contacts in the future.