Vaccination of Man Against the Virus of Equine Encephalomyelitis (Eastern and Western Strains)

A group of 100 men and women have been vaccinated with the crude formolized chickembryo-vaccines of the sort employed in the protection of horses against equine encephalomyelitis. A bivalent vaccine effective against both Eastern and Western strains of virus was used. General and local reactions to the vaccine-material were mild or absent except in one instance in which muscular stiffness developed subsequent to vaccination. Response to the vaccines as measured by serum-neutralizing antibody-content was high and apparently more rapid for the Western strain antigen than for the Eastern. With the former, high titers were observed seven days after the first injection while comparable titers for the latter were found after fourteen days. The results yield no contraindications to the use of properly prepared and tested vaccines of this nature in man. On the contrary, the findings together with consideration of the demonstrated prevalence of subclinical and clinical infections with both strains of virus constitute emphatic indications for the vaccination of people frequently exposed to the virus in the laboratory and in the field.