An attenuated influenza virus vaccine: protection against homologous and heterologous strains of virus

A clinical trial with Alice/R-75 strain, live attenuated serum inhibitor-resistant intranasal bivalent influenza A/B vaccine

A clinical trial was conducted with Alice/R-75 strain live attenuated intranasal influenza A/B vaccine. With double blind control 88 adult volunteers were administered 2 doses of Alice/R-75 vaccine, 93 volunteers received one dose of Alice/R-75 vaccine and one dose placebo solution and 94 subjects were administered 2 doses of placebo solution. Twenty-three other subjects received Alice strain monovalent influenza A vaccine. For comparison, data from 21 subjects who received monovalent intranasal R-75 strain influenza B in two doses is included. The vaccine was generally well tolerated. Four-fold serum hemagglutination-inhibiting (HAI) antibody titer rises to A/England/42/72 occurred in 39% of the monovalent Alice strain vaccines; in contrast 18% of those given 2 doses of bivalent Alice/R-75 vaccine and 11% of those given 1 dose of bivalent vaccine had similar four-fold HAI antibody titer rises. HAI antibody titer rises to influenza B/Hong Kong/72 occurred in 38% of R-75 strain monovalent vaccinees, 14% of Alice/R-75 2-dose vaccinees and 11% of Alice/R-75 one dose vaccinees. An epidemic of influenza at onset of the study made evaluation of the efficacy of the vaccine impossible.

Trials of live influenza A recombinants in man during natural antigenic change in 1971-1976

A long-term study is described of human trials with live recombinants derived from A/PR/8/34 (H0 N1) and successive virulent H3 N2 viruses. A/PR/8/34 was noninfectious for man and the H3 N2 strains all induced similar influenza-like illness. In each recombinant experiment, some of the progeny were adequately attenuated and potentially immunogenic. In addition, there appeared to be evidence of probable cross-protection against viruses with related but non-identical haemagglutinins. However, the degree of cross-protection depended upon the time interval between the appearance of the epidemic and vaccine viruses. Recombinants of A/PR/8/34 and a human Hsw1 strain of low virulence did not function satisfactorily, and it seemed that the suitability of A/PR/8/34 as a 'master' parent depended upon the presence of standard genetic properties in the wild parents. The replacement of A/PR/8/34 with the partially virulent virus, X-31 (H3 N2), produced a live vaccine which was infectious but poorly antigenic. A universal master strain for live influenza vaccine recombinants is probably not yet a practical possibility.