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Alfred Paul Bay, M.D.; Manning I. Sankstone, M.D.
JAMA. 1940;115(6):475. doi:10.1001/jama.1940.02810320055025.
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To the Editor:—  In the Illinois Medical Journal for January 1940, Dr. R. D. Barnard reports the case of a blood donor who after many successively negative serologic examinations suddenly became Wassermann positive. It was suggested that the change in reaction was due to the presence of vaccinia. Since vaccination and serologic testing is a routine procedure at this institution, it was an easy matter to make a statistical examination of this fact. One hundred patients (fifty male and fifty female) with known recent negative serologic reactions were vaccinated and the blood Kahn tests repeated at intervals varying between twenty-nine and seventy-six days from the onset of the vaccination take. In no instance was a positive Kahn reaction obtained. We conclude from this that if vaccinia produces a positive blood Kahn reaction it does so in less than 1 per cent of cases and that therefore patients with vaccinia and


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