High immunogenicity of measles AIK-C vaccine produced in Vietnam

The goal of measles elimination has been set for 2012 in the WHO Western Pacific Region. To achieve this goal, an enhanced immunization strategy is required, and measles vaccines have been provided through the Expanded Programme on Immunization (EPI) in Vietnam. A large quantity of vaccines should be supplied for a two-dose immunization schedule with a supplementary catch-up campaign. The live measles vaccine AIK-C strain was produced in Vietnam through technical transfer from the Kitasato Institute, Japan. PolyVac I was produced from bulk materials imported from Japan and PolyVac II from the AIK-C seed. Two clinical trials were conducted using three vaccines: PolyVac I, and II, and the EPI vaccine (Rouvax) for the control. A total of 160 subjects were examined for the immunogenicity of PolyVac I and 57 for that of the EPI vaccine. All subjects became sero-converted in PolyVac I groups for three different Lots, but 54 (94.7%; 88.9-100%) of 57 recipients of the EPI vaccine became sero-positive. For PolyVac II, 118 initially sero-negatives became sero-converted. Whereas, 107 (95.5%; 91.7-99.3%) of 112 initially sero-negatives in the EPI group showed sero-conversion. The mean titers of post-immunization sera of sero-converted subjects receiving PolyVac I and II were lower than that for the EPI vaccine. No significant difference was observed in the incidence of adverse clinical events. Essentially the same results were obtained using PolyVac I and II, showing higher sero-conversion rates than the EPI vaccine, and PolyVac measles AIK-C will be favorable in Vietnam and Southeast Asian countries.