BCG vaccination and leukemia mortality.

In Chicago from 1964 through 1969, one death from leukemia was recorded among 54,414 infants 0 through 6 years of age, who were vaccinated at birth with BCG vaccine, a rate of 0.31/100,000/yr. In contrast, among 172,986 infants of a similar age and race who were not vaccinated, 21 deaths were reported, a rate of 2.02/100,000/ yr. The difference is statistically significant (P =.04) and suggests the value of BCG vaccinations in preventing leukemia in children, but since this is a retrospective study, no firm conclusions can be drawn.