What is the description of Bacillus Calmette-Guérin (BCG)?

From the Guidelines

BCG (Bacillus Calmette-Guérin) is a vaccine primarily used to protect against tuberculosis (TB), but it's also an effective immunotherapy treatment for bladder cancer. As a TB vaccine, BCG contains a live attenuated strain of Mycobacterium bovis that stimulates the immune system to develop protection against Mycobacterium tuberculosis without causing the disease [ 1 ]. For bladder cancer treatment, BCG is instilled directly into the bladder through a catheter, typically once weekly for six weeks initially, followed by maintenance treatments for up to three years depending on risk factors.

Key Points

• The standard dose is usually 50-81 mg of BCG suspended in 50 mL of saline.
• BCG works by triggering a local immune response that attacks cancer cells in the bladder lining.
• This immune activation involves multiple mechanisms including the recruitment of T cells, natural killer cells, and macrophages that recognize and destroy cancer cells [ 1 ].
• Side effects can include urinary frequency, painful urination, blood in urine, and flu-like symptoms.
• In rare cases, serious infections can occur, so patients should report persistent fever or other concerning symptoms immediately [ 1 ].
• BCG is particularly effective for treating high-grade non-muscle invasive bladder cancer and carcinoma in situ, with success rates of 50-70% in preventing recurrence.

Administration and Reactions

• BCG vaccination often results in local adverse effects, such as moderate axillary or cervical lymphadenopathy and induration and subsequent pustule formation at the injection site [ 1 ].
• More severe local reactions include ulceration at the vaccination site, regional suppurative lymphadenitis with draining sinuses, and caseous lesions or purulent drainage at the puncture site.
• Normal reactions to the vaccine are characterized by the formation of a bluish-red pustule within 2-3 weeks after vaccination, which then ulcerates and forms a lesion [ 1 ].

Recommendations

• BCG vaccination should be considered for infants and children who reside in settings in which the likelihood of M. tuberculosis transmission and subsequent infection is high [ 1 ].
• BCG vaccination may be considered for health-care workers who are employed in settings in which the likelihood of transmission and subsequent infection with M. tuberculosis strains resistant to isoniazid and rifampin is high [ 1 ].
• BCG is not recommended for children and adults who are infected with human immunodeficiency virus because of the potential adverse reactions associated with the use of the vaccine in these persons [ 1 ].

From the Research

BCG Description

• BCG (Bacillus Calmette-Guérin) is a vaccine primarily used against tuberculosis (TB) [(2,3,4,5,6)].
• It has been shown to have high efficacy against childhood tuberculous meningitis and miliary tuberculosis, but variable efficacy against adult pulmonary tuberculosis and other mycobacterial diseases 2.
• BCG vaccination is a highly cost-effective intervention against severe childhood tuberculosis, with an estimated cost of US$2-3 per dose and US$206 per year of healthy life gained 2.

Mechanisms and Applications

• BCG has non-specific immune-enhancing effects, offering protection against various pathogens beyond TB [(3,5,6)].
• Recombinant BCG (rBCG) technology has been used to create rBCG vaccines expressing heterologous antigens, targeting a range of bacterial, viral, and parasitic diseases 3.
• BCG-induced protection against Mycobacterium tuberculosis infection involves mechanisms such as alternative T cell responses, antibody-mediated protection, and innate immune mechanisms, including trained immunity [(5,6)].

History and Future Directions

• BCG was developed 100 years ago and remains the only licensed TB vaccine and the most frequently administered vaccine worldwide [(4,5)].
• Despite its widespread use, the burden of TB remains high, and efforts are being made to improve BCG's efficacy, including alternative vaccination routes, BCG revaccination, and the use of recombinant BCG vaccines [(4,5)].
• BCG's potential to confer trained immunity and offer benefits for the control of new and emerging infectious diseases, such as COVID-19, is being explored 5.