Investigations on allergic and serological reactions following inoculation of inactivated smallpox vaccines by cutaneous scarification.

A number of 154 young adults were given a smallpox vaccine inactivated by UV (103 subjects) or by 4degrees/00 formol (51 subjects). Inoculation induced an early cutaneous reaction in 75.4% of the revaccinated subjects. The incidence of positive HAI reactions in this group increased from 30.2% before vaccination to 63.8% after inoculation, while the geometric mean titer increased from 2.88 to 10.73. This would prove the early reactions to be allergic responses of organisms sensitized against smallpox vaccine, capable of stimulating antibody formation. No cutaneous reaction was recorded in the 7 persons vaccinated for the first time (without pre-existent cutaneous scars). These subjects developed neither cutaneous nor humoral response to the killed virus, as there was no previous sensitization to the respective antigen.