WRL 105 strain live attenuated influenza vaccine; comparison of one and two dose schedules.

Haemagglutinating inhibiting antibody (HAI) responses were determined and clinical reactions recorded in 162 adult volunteers who received either 1 or 2 intranasal doses of 10(7-0) EID50 WRL 105 strain live influenza vaccine or placebo. After administration of a single dose of vaccine significant antibody responses were obtained in 69 (70%) of 98 volunteers with initial antibody titres of less than or equal to 1/20. Of the 70 volunteers who received a second dose of vaccine, 62 provided a further post-vaccination sample of serum, and only 3 (4-8%), who had not responded to the first dose of vaccine, produced a significant antibody response. Local, upper respiratory and constitutional symptoms were recorded more frequently after the administration of a first dose of vaccine than after placebo or a second dose of vaccine. The symptoms were of a minor nature except in one volunteer who, after the first dose of vaccine, developed influenzal symptoms followed by bronchitis.