Immunization of institutionalized asthmatic children and patients with psychomotor retardation using live attenuated cold-adapted reassortment influenza A H1N1, H3N2 and B vaccines.

Live attenuated cold-adapted reassortant (CR) influenza virus vaccines were evaluated in institutionalized asthmatic children and severe psychomotor-retarded (SPR) patients. Almost all the vaccinees were seropositive to the vaccine strains before immunization. Trivalent CR vaccine (containing A H1N1 (CR-125), A H3N2 (CR-149) and B (CRB-117)), bivalent CR vaccine (CR-125 and CR-149) and monovalent CRB-117 were inoculated to 19 asthmatic children and 36 and 16 SPR patients, respectively. Overall 49, 22, and 11% of vaccinees were infected by A H1N1, A H3N2 or B vaccine viruses, respectively, as indicated by significant haemagglutination-inhibition (HI) antibody titre rises 4 weeks after inoculation. No severe adverse reactions associated with CR vaccination were observed in the handicapped patients. A nosocomial outbreak of influenza A H1N1 occurred in the ward with asthmatic children, but none of the 19 CR-trivalent vaccinees became infected. However, five of 20 non-vaccinees in the same ward, and ten of 30 vaccinees in another ward that received inactivated split vaccine became infected. The CR vaccines demonstrated significant protective effects against natural exposure to the A H1N1 virus, and were well tolerated and safe when given to patients with bronchial asthma and severe psychomotor retardation.