Significance of the number of viable units in BCG vaccines.

The objective of the study was to establish the incidence of suppurative lymphadenitides in newborns vaccinated with BCG vaccines of different strength and to investigate the postvaccination tuberculin positivity of the children involved in the study. Lyophilized vaccines prepared from the Pasteur strain were used. Altogether 51,000 children were included in the study. One group, consisting of 30,000 newborns was vaccinated with a BCG lot containing 2 X 10(5) viable units (VU) per dose. The other group, consisting of 21,000 newborns, was given a BCG lot containing 0.5 X 10(5) VU per dose. The incidence of suppurative lymphadenitides per 1,000 vaccinated infants was 6.84 and 0.87 in the two groups, respectively. Tuberculin tests were carried out 2 years after the vaccination. Two units of RT-23 tuberculin were used. In 3,821 children vaccinated with the stronger vaccine the rate of tuberculin positivity was found to be 19.8 per cent, while it was 16.4 per cent among 5,035 children who had been given the weaker lot.