Abstract
In their preceding paper the authores reported that an attenuated strain of A2/HK influenza virus had been obtained by the adaptation of virus to growth at 28°C in embryonated eggs. In the present paper, the responses of volunteers administered with this cold-adapted strain of influenza virus were described. A live vaccine was prepared by differential centrifugation from the infected allantoic fluid of leukovirusfree SPF eggs. The volunteers were 18 to 62 years old and divided into three groups. The first group received 0.5ml of a commercially available inactivated influenza vaccine subcutaneously and, a week later, 0.3ml of this live vaccine nasopharyngeally. The second group received 0.5ml of the inactivated vaccine subcutaneolusly and, a week later, 0.3ml of placebo vaccine (PBS) nasopharyngeally. The third group received 0.3ml of the inactivated vaccine nasopharyngeally and, a week later, 0.3ml of the live vaccine nasopharyngeally.
Sera were collected from all the groups and examined for HI antibody. Antibody response was determined by the percentage showing a fourfold or greater rise in titer and by an increase in geometric mean titer. After the final vaccination, 45% of the sera developed an antibody response (geometric mean titer rising from 26.5 to 27-9) in the first group, 20% in the second group, and 40% in the third group. The majority of those who had been inoculated with the live vaccine manifested no clinical symptoms. It was also revealed that the live vaccine was effective for stimulating a local IgA response.
