Abstract
The Bacillus Calmette–Guérin vaccine (BCG) has been associated with beneficial non-specific effects (NSEs) on infant health. Within a randomized trial on the effect of neonatal BCG on overall health, we investigated the possible immunological impact of neonatal BCG vaccination on lymphocyte subsets, determined by flow cytometry. In 118 infants blood samples were obtained 4 (±2) days post randomization to BCG vaccination or no intervention, and at 3 and 13 months of age. No effects of BCG were found at 4 days. However, BCG increased proportions of effector memory cells at 3 months (Geometric mean ratio (GMR) 1.62, 95% confidence interval (CI) (1.20–2.21), p = 0.002 for CD4+ T cells and GMR 1.69, 95% CI (1.06–2.70), p = 0.03 for CD8+ T cells), and reduced proportions of late differentiated CD4+ T cells (GMR = 0.62, 95% CI (0.38–1.00), p = 0.05) and apoptotic CD4+ T cells at 13 months (GMR = 0.55, 95% CI (0.32–0.92), p = 0.03). In conclusion, limited overall impact of neonatal BCG vaccination on lymphocyte subsets was found in healthy Danish infants within the first 13 months of life. This is in line with the limited clinical effects of BCG observed in our setting.
Highlights
The primary estimate of the Bacillus Calmette-Guérin vaccine (BCG) effect is presented as the geometric mean ratio (GMR) with 95% confidence interval (CI) obtained as the anti-logged coefficient from a linear regression with the log-concentration or log-proportion as outcome and randomization group as covariate
The following predefined potential effect modifiers were assessed: age at randomization and maternal BCG
At age 3 months, we found proportions of TEM to be higher in the BCG group compared to controls for both CD4+ T cells (GMR 1.62, 95% CI (1.20–2.21), p = 0.002) (Fig. 4A) and CD8+ T cells (GMR 1.69, (1.06–2.70), p = 0.03) (Table 1)
Summary
Limited overall impact of neonatal BCG vaccination on lymphocyte subsets was found in healthy Danish infants within the first 13 months of life. This is in line with the limited clinical effects of BCG observed in our setting. The observation that BCG may have beneficial non-specific clinical effects (NSEs) beyond the specific protection against TB dates back to the 1930s2, and today BCG is used in standard treatment of bladder cancer Both observational studies[3,4,5,6] and recent randomized clinical trials[7,8] from low-income countries found that neonatal BCG vaccination reduced all-cause morbidity and mortality from infections other than TB. Induce a nonspecific response to non-mycobacterial infections mediated by heterologous Th1/Th17 responses[14], representing yet another potential biological mechanism which could explain NSEs
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