Small-scale field trial with neuraminidase vaccine.

An inactivated whole-virus vaccine was prepared from the influenza virus recombinant H0N2 and administered to two groups of subjects. A total of 1,200 subjects were vaccinated; comparable groups of subjects served as controls. From a portion of the vaccinees sera were obtained prior to vaccination and three to four weeks afterwards. Serological tests revealed development of or increase in the antibody against H0 in a great majority of the vaccinated subjects and against N2 in slightly more than half of them. Antibody response to H3 antigen was only rarely encountered. Approximately three months after vaccination an influenza epidemic caused by Victoria-like (H3N2) viruses broke out in Czechoslovakia. Numerous influenza cases occurred in the two populations followed. Morbidity was significantly lower among the vaccinated than among the control subjects, indicating a protective effect of the neuraminidase vaccine under field conditions.