Comparative study of the smallpox vaccines from B-51, EM-63 and L-IVP in a controlled epidemiological experiment. II. The characteristiics of the immunogenicity of the smallpox vaccines]

Immunogenicity of smallpox vaccines prepared of EM-63, L-IVP, and B-51 strains was studied under conditions of strict controlled epidemiological trial. Skin reactions to revaccination and vaccines antigenic activity indices were detemined in the persons vaccinated. Changes in the virus-neutralizing and antibodies suppressing hemagglutination was the same in persons vaccinated with any of the preparations tested. The maximal virus-neutralizing antibodies level was determined 1 month after the vaccination and persisted without any essential changes for one year. The titre of hemagglutination inhibiting antibodies also reached the maximum in one month, but diminished gradually by the end of one year after the vaccination. There were found no significant differences in the antigenic activity of the vaccines. The vaccines studied also displayed no difference in the number and character of skin reactions to revaccination. In comparing the antibodies level and the character of skin reactions to revaccination it was found that the titres of hemagglutination inhibiting antibodies and virus-neutralizing antibodies of 1:40 and over were in the great majority of cases determined in the blood sera of the vaccinated persons with the immediate and negative reactions to revaccination, i. e. in those with intensive postvaccinal immunity.