Bacille Calmette-Guérin vaccination at birth and differential white blood cell count in infancy. A randomised clinical trial

Background The Bacille Calmette-Guerin (BCG) vaccine against tuberculosis (TB) may have beneficial non-specific effects (NSEs) beyond the protection against TB. This may be related to modifications of the innate immune system. We investigated the effect of BCG at birth on differential white blood cell (WBC) count in healthy, Danish infants. Method The Danish Calmette Study randomised newborns to BCG at birth (Danish strain 1331, Statens Serum Institut) or no intervention. A sub-group of infants had blood samples collected 4 days after randomisation (n = 161), and at age 3 months (n = 152) and 13 months (n = 300). We evaluated the effect of BCG on WBC differential count (total leucocytes, lymphocytes, monocytes, eosinophil, neutrophil and basophil granulocytes (109 cells/L)) measured in peripheral blood. Results Overall, we found no effect of BCG on differential WBC counts at any time point. Conclusion BCG at birth did not affect WBC count in our cohort of healthy, Danish infants.