Measles vaccination. VIII. The occurrence of antibodies against virus envelope components after immunization with inactivated vaccine. Effects of revaccination with live measles vaccine.

Children immunized with 4 doses of formalin-inactivated vaccine and/or purified hemagglutinin prepared from Tween 80-ether (TE) treated material were subjected to a follow-up 8-9 years after the last dose of vaccine. 11 out of 27 children had clinical and/or serological signs of infections with wild measles virus during the 8 to 9 years post-booster period. 10 out of the 11 children with infections had non-hemagglutinating-inhibiting (HI) hemolysis-inhibiting (HLI) antibodies demonstrable in their sera after removal of HI antibodies by absorption with TE antigen. In contrast 13 out of 16 vaccinees without detectable signs of infection lacked non-HI HLI antibodies. 10 out of these 13 children were vaccinated with further attenuated live measles virus. There were no clinical reactions to faccination. 4 vaccinees with low pre-vaccination HI antibody titers showed significant rises of antibody titers including non-HI HLI antibodies. In the remaining children no take of the live vaccine could be demonstrated. Thus HI antibodies of a certain minimal concentration can block the replication of vaccine virus even in the absence of non-HI HLI antibodies. However, since it will be difficult to establish these conditions by sue of available inactivated vaccines it is recommended that future vaccine products should include both major virus envelope surface components, the hemagglutinin and the hemolysin.