The influence of BCG on vaccine responses - a systematic review

INTRODUCTION: Bacillus Calmette-Guerin (BCG) vaccine is one of the most widely used vaccines worldwide. In addition to providing protection against tuberculosis, it has non-specific (heterologous) immunomodulatory effects. AREAS COVERED: In our systematic review, we found eight studies, involving 2439 participants, investigating the influence of BCG vaccination on the humoral response to 16 different vaccines. A beneficial effect of BCG on vaccine responses was reported in five of the eight studies. Previous or concurrent administration of BCG was associated with significantly higher levels of antibodies against hepatitis B, polio type 1, pneumococcus, and influenza in some studies. No study reported a statistically significant increase in the response to other vaccines, though in many cases higher antibody levels were observed in the BCG-vaccinated group. One study reported lower levels of antibodies against hepatitis B in BCG-vaccinated participants. EXPERT COMMENTARY: The studies in this review suggest that BCG modulates humoral responses to other vaccines. Future studies should focus on the influence of BCG vaccine strain and the optimal timing of administration to exploit the immunomodulatory effects of BCG to improve vaccine efficacy and duration of protection.