DOES THE PROTECTIVE EFFECT OF NEONATAL BCG CORRELATE WITH VACCINE-INDUCED TUBERCULIN REACTION

A case-control study was conducted in Saudi Arabia, where the same str ain of BCC has been used and surveys had shown that up to 88% of vacci nated children remain tuberculin negative. Active cases were obtained by surveying the seven tuberculosis centers in 1 yr. Control subjects were obtained from a nationwide survey of normal individuals. Vaccinat ion in both groups was ascertained by history and BCG scar. Relative r isk of contracting active tuberculosis in the vaccinated versus unvacc inated and protection was calculated. protection was as follows: age g roup 5 to 14 yr, 82% (55 to 93%); age group 15 to 24 yr, 67% (55 to 77 %); and age group 25 to 34 yr, 20% (-6 to 37%). We document the uninte rrupted record of protection by BCC administered in the neonatal perio d and discuss the significance of vaccination timing. We concur with o ther studies that protection lapsed after about 20 yr. More importantl y, this is the first large study that documents a lack of tuberculin s ensitivity despite protection. This challenges the view that sensitiza tion is essential for protection and supports the ''two-pathway'' theo ry that BCC vaccination could trigger either protective (Lister type) or antagonistic (tuberculin or Koch type) reactions and that the most protective vaccines would have little tuberculin-sensitizing effect be cause the two pathways are competitive.