Vaccine Prepared from Chicken Embryo Cultures for Immunization Against Smallpox

Abstract

The effect of cultivation in chicken-embryo medium on the potency of a dermal strain of vaccine virus, and the properties of vaccines prepared from these tissue cultures have been studied. The potency of the virus decreased after prolonged cultivation in vitro but was reestablished by passage through the testicles of rabbits. Vaccines containing 50% glycerol retained their potency for 12-20 mos. when stored at from 3 to [long dash]5[degree] C under anaerobic conditions. These vaccines, when tested in 23 unvac-cinated children, induced characteristic reactions, but the % of "takes" after inoculation by the multiple-puncture or single-scratch method was lower than is usually obtained with calf lymph.