BCG vaccine: The century-old Shot Leaving a Mark, But Not Widely Used in the U.S.
Geneva,Switzerland - A vaccine that leaves a visible scar on the arm,used globally for nearly a century,remains a subject of scientific debate and isn’t routinely administered in the United States. The Bacillus Calmette-Guérin (BCG) vaccine, first used to immunize humans in 1921 in Paris, is the world’s oldest vaccine still in use, but its effectiveness against tuberculosis (TB) is ”controversial” due to conflicting data, according to the World Health Organization (WHO).
The BCG vaccine is designed to provide immunity against TB, but the presence of the characteristic scar it leaves after injection is not an indicator of immunity. “After a few months,the local reaction generates a small scar. The presence of a typical scar is used as an indicator of previous anti-tuberculosis vaccination, but it is indeed not an indicator of immunity against tuberculosis,” the WHO clarifies.
Despite this,the WHO continues to recommend a single dose of BCG for newborns - or as soon as possible after birth – in countries with a high prevalence of tuberculosis. This is notably true for children who do not exhibit the typical scar, indicating they haven’t been previously vaccinated. “In countries with a high morbidity burden, vaccination against tuberculosis is recommended for children who do not have the characteristic scar,” the WHO states.
However, the vaccine’s protection isn’t guaranteed. The Centers for Disease Control and Prevention (CDC) notes that individuals can still contract TB even after receiving the BCG vaccine, as its protective effects diminish over time. WHO data suggests protection after neonatal vaccination “is commonly considered to gradually decrease until reaching non-notable levels after between 10 and 20 years.”
While the BCG vaccine doesn’t prevent primary infection or reactivation of latent lung infection – the primary source of TB spread – it does offer documented protection against severe forms of the disease in children, specifically tuberculous meningitis and disseminated tuberculosis. The WHO acknowledges that “the effect of BCG vaccines on the transmission of M. tuberculosis is, thus, limited.”
Why isn’t BCG widely used in the U.S.?
The United states has a relatively low incidence of TB compared to many other parts of the world. Because of this, and the vaccine’s inconsistent efficacy, the CDC does not currently recommend routine BCG vaccination. Public health efforts in the U.S. focus on early diagnosis, directly observed treatment, preventative treatment, and robust infection control measures. As the WHO concludes, “until an improved tuberculosis vaccine is available, the fight against the spread of tuberculosis will continue to rely on the tools currently available.”
Beyond TB, the BCG vaccine also demonstrates effectiveness against leprosy and Buruli ulcer, and is even used in some bladder cancer treatments. However, the WHO clarifies that controlling these diseases isn’t the primary objective of BCG vaccination programs.
