The reactogenicity and immunogenicity of combined measles and rubella (MR) booster vaccination, via aerosol and subcutaneous routes, was assessed in 562 healthy children. Rates of rubella seroconversion and geometric mean titers (GMT) were similar for both routes. Rates of measles PN seroconversion, GMT and measles ELISA post-vaccination seropositivity and seroconversion rate were each higher for aerosol vaccine (54%, 3928 IU/l, 99.6 and 98.8%), than for subcutaneous vaccine (7%, 866 IU/l, 92.2 and 82.4%) (P<0.01). Reactogenicity was higher for subcutaneous vaccine (P<0.05). This study demonstrates that aerosol vaccine was more immunogenic for measles antibodies, and equally immunogenic for rubella antibodies. Aerosol vaccine was less reactogenic.