Protective Effect of Vaccination Against Induced Influenza B. ∗

Abstract

In the previous paper 1 evidence was presented to show that subcutaneous inoculation of vaccine containing concentrated and inactivated influenza virus, Types A and B, was followed by an increased resistance of human individuals, as measured by the febrile response, to a subsequent intranasal spray of active Type A influenza virus. The present report deals with the results of a similar study of the effect of subcutaneous vaccination upon resistance of another group of individuals in the same institution to infection with influenza virus, Type B.

The vaccine was the same material employed in the study with influenza A. The subjects were 96 physically active male residents of another ward of the Ypsilanti State Hospital, Ypsilanti, Michigan.

On December 21, 1942, 46 of the men received 1.0 cc of the vaccine subcutaneously. On April 13, 1943, 19 of the same individuals received a second injection of 1.0 cc of the vaccine and 23 men not previously vaccinated now received 1.0 cc of the vaccine. There remained 27 men vaccinated in December but not since, and 23 control subjects who had not at any time received vaccine.

On May 10, 1943, 27 days after the administration of vaccine to 2 of the groups, all 96 men received the Lee strain of influenza B virus by intranasal inhalation. The virus from the allantoic fluid of the infected hen's egg had been concentrated 2 tenfold in physiological salt solution. The material was sprayed for 5 minutes under 10 lb air pressure from a nebulizer so as to deliver approximately 0.5 cc of the virus. Oral temperatures had been recorded twice prior to the inhalation of the virus and were continued twice daily thereafter. Records were kept of signs or symptoms of illness.