1. Being born in Mexico
    I have this scar on my shoulder from since I was a baby, as does my mom and sister. I've known it's from a vaccination my whole life.
  2. Many baby boomers have a similar scar
    However, (most of) theirs is from the smallpox vaccine. The US stopped smallpox vaccinations in 1972 (because it was eradicated). The rest of the world had stopped these vaccinations by 1986.
  3. My scar is from BCG vaccine
    BCG stands for Bacillus Calmette-Guérin, it's meant to protect from human tuberculosis.
  4. BCG vaccine is used in countries with high tuberculosis rates
    The US has a really low tuberculosis rate, Mexico on the other hand has a high tuberculosis rate.
  5. After being vaccinated with BCG (as well as smallpox vaccine) a pustule forms on the skin
    After the pustule opens and drains a scar will develop on the person. The size of the scar depends on the inflammation caused by the immune response and how well they heal.
  6. Giphy