Neonatal BCG-vaccination has no effect on recurrent wheeze in the first year of life. A randomized clinical trial

Abstract Background Recurrent wheeze is frequent in childhood. Studies have suggested that Bacillus Calmette-Guérin (BCG) vaccination may have non-specific effects, reducing general non-tuberculosis morbidity, including respiratory infections and atopic diseases. The mechanisms behind these non-specific effects of BCG are not fully understood, but a shift from Th2 to Th1-response has been suggested as a possible explanation. Objective We hypothesized that BCG at birth would reduce the cumulative incidence of recurrent wheeze during the first year of life. Methods The Danish Calmette Study is a multicenter randomized trial conducted from 2012-2015 at three Danish hospitals. The 4262 newborns of 4184 included mothers were randomized 1:1 to BCG (SSI strain 1331) or to a no-intervention control group within 7 days of birth; siblings were randomized together as one randomization unit. Exclusion criteria were gestational age