BCG vaccination strategies against tuberculosis: updates and perspectives.

Bacillus Calmette-Guérin (BCG) is the only licensed vaccine against tuberculosis (TB). However, BCG has variable efficacy and cannot completely prevent TB infection and transmission. Therefore, the worldwide prevalence of TB calls for urgent development of a more effective TB vaccine. In the absence of other approved vaccines, it is also necessary to improve the efficacy of BCG itself. Intravenous (IV) BCG administration and BCG revaccination strategies have recently shown promising results for clinical usage. Therefore, it is necessary for us to revisit the BCG vaccination strategies and summarize the current research updates related to BCG vaccination. This literature review provides an updated overview and perspectives of the immunization strategies against TB using BCG, which may inspire the following research on TB vaccine development.