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The BCG vaccine or Bacillus Calmette-Guérin vaccine is a vaccine primarily used against tuberculosis (TB). It is named after the bacteriologists Albert Calmette and Camille Guérin who developed it in the 1920s. While the vaccine does not provide total protection from contracting TB, it effectively prevents severe forms of the disease, such as TB meningitis in children. It is on the World Health Organization's List of Essential Medicines.

Historical Development

Albert Calmette, a physician, and Camille Guérin, a veterinarian, developed the BCG vaccine at the Pasteur Institute in Lille, France. The duo used a strain of Mycobacterium bovis, which they weakened by culturing it in bile for 13 years, leading to a total of 230 serial passages. The first human trials of the BCG vaccine were initiated in 1921.

Indications and Usage

The BCG vaccine is indicated for the prevention of tuberculosis, specifically in populations or individuals who are at high risk. This includes countries with high prevalence rates and children who are at high risk of exposure to multi-drug resistant TB. It is typically administered to infants, but may also be used for adolescents and adults who are tested and found to be without TB infection.

Effectiveness

The effectiveness of the BCG vaccine can vary significantly. It has been shown to be very effective (about 80%) against severe forms of TB, such as miliary TB and tuberculous meningitis, in children. However, its effectiveness against pulmonary TB in adults is variable, ranging from 0 to 80%. Factors that can influence the vaccine's effectiveness include genetic differences in populations, exposure to environmental mycobacteria, and variations in the BCG strains used.

Administration

The BCG vaccine is typically given as a single dose, injected into the upper arm's skin layer. The vaccination leaves a small scar at the injection site, which can often serve as a tell-tale sign of BCG vaccination.

Side Effects and Contraindications

The BCG vaccine is generally well-tolerated. Common side effects are mild and can include fever, irritability, and pain and swelling at the injection site. In rare cases, severe complications such as a BCG infection may occur.

The vaccine should not be given to individuals who have a weakened immune system, such as those with HIV/AIDS or those receiving immunosuppressive therapy. Additionally, it is contraindicated in individuals with a known hypersensitivity to any component of the vaccine.

Future Research

Research is ongoing to improve the BCG vaccine's effectiveness against pulmonary TB and to extend its efficacy to adults. Modified versions of the vaccine and entirely new vaccines against TB are currently under development.

See also

• Tuberculosis
• Vaccine

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