Vaccine scars spark social media discussion

Social media users have recently shared numerous photos of a distinct, circular scar on the upper arm, sparking widespread curiosity regarding its origin. Medical experts explain that these marks are typically the result of specific vaccination methods used to combat smallpox or tuberculosis.

The smallpox vaccine often utilized a bifurcated needle that pricked the skin multiple times, triggering a localized immune response and subsequent scarring. Alternatively, the Bacille Calmette-Guérin (BCG) vaccine, used to protect against tuberculosis, is a common cause of similar permanent marks. The BCG vaccine is widely administered in approximately 150 countries, including China, Indonesia, and Argentina.

In the United States, the Centers for Disease Control and Prevention (CDC) notes that the BCG vaccine is not part of a universal infant program because tuberculosis remains relatively rare domestically, with only three cases per 100,000 people recorded last year. The vaccine is generally only recommended for individuals meeting specific criteria in consultation with medical experts.