It is not yet clear from these recent volunteer studies (8) and from the results of Merigan et al. (14) what the optimal method and schedule for administering HuIFN should be. Taken together, the results with relatively low doses of interferon (1 to 4 X 10(6) units) plus antihistamine pretreatment, and with multiple doses of HuIFN alpha (total 14 X 10(6) units) indicate the need for better methods of delivery. However, it is of interest that protection was achieved by extremely small amounts of HuIFN alpha protein - Merigan (14) used only about 160 mcg. We anticipate that with better supplies of interferon from HuIFN genes cloned in bacteria, we may seek more efficient means of delivery and obtain better protection of volunteers against respiratory virus infections.