Vaccination of Human Subjects with Virus of Human Influenza

Abstract

The immunization of ferrets and mice 1 , 2 with human influenza virus has been reported. When injected into these animals by the subcutaneous or the intraperitoneal routes the virus elicits no evidence of infection, but the animals so treated develop circulating antibodies against the virus and become actively resistant to the infectious agent introduced by the intranasal route. More recently it has been possible to demonstrate the same effects with virus grown outside the animal body in tissue culture medium. 3 , 4

The successful cultivation of the virus in artificial medium immediately eliminated many of the undesirable features, such as the possibility of bacterial contaminants, extraneous viruses, etc., which constantly attend the use of virus from infected animals for studies in human individuals. After preliminary tests upon 3 human subjects which demonstrated that the artificially cultivated virus injected subcutaneously produced no serious reactions, a group of adult human volunteers was selected to determine the immunizing capacity of culture virus.

From among the subjects available, those individuals were selected whose serum beforehand exhibited the least protective power against the human influenza virus, as measured by its capacity to protect white mice against a high concentration (10% suspension) of mouse passage virus. From each individual a sample of serum was obtained immediately before the first injection of virus and again before each subsequent inoculation.