Laboratory studies on a strain of Asian influenza virus used as a living vaccine. (A report to the Medical Research Council Committee on Influenza and other Respiratory Virus Vaccines)

Two pools of living influenza vaccine derived from the Russian A 2 strain Iksha had given discrepant results in clinical trials. The less effective pool showed an increased thermostability of haemagglutinin, an increased elution rate from red blood cells and a reduced ability to grow in chorioallantoic membranes at temperatures above 40° C. The relationship of these findings to the virulence of influenza viruses is discussed.