Strange markings

It began at the start of summer, when the layers of clothing began to shed. When we moved from five layers to four, to three to two, and now, at the height of summer, the lightest material passable for appropriate for work clothing.  I noticed one of my students had strange markings on her shoulder. I began counting, one dot, two, three. There were 18 dots in total.  Two square boxes of 9 dots a piece. I began to inspect all of my children. Almost everyone of them had it.
"What are these markings?" I asked my Korean co-workers.
It was explained, that these markings were a new form of a vaccination.  Previous to this currently used vaccination, the out-dated one, left a scar on the shoulder.  This newer vaccination was created to avoid that permanent scarring.  It is said, that the markings will fade with years.
Now, I was even more confused.  Where was my scar I wondered? I'd had all my shots as a child, and even more shots before I left for traveling the world. My family were not one of the anti-vaccine families, so why was it that all of my international friends had scars on their arms, and I didn't nor did any of my American friends. But no one could tell me even what vaccine it was, that is until recently. I follow a blog called, Ask a Korean.
Basically, people write him their questions and he answers them.  Very useful site for questions regarding Korean culture.  He explained, that this vaccine is the BCG vaccine, and for some reason Americans do not receive it.
Evidently, we are one out of two countries in the world that do not recommend it for children. (The Netherlands is the other) Tuberculosis (TB)  kills more people in the world than any other infection. Currently, it infects 1.6 billion people, about one-third of the world's population.  But the vaccine, that is used, does not protect against the kind that is the true killer, which is the millary TB. The TB vaccine is good at protecting against the severe form of disease found in young children (called "miliary" TB), but not as good at protecting against the lung infection commonly found in adolescents and adults. Because miliary TB is very uncommon in the United States, we do not use the TB vaccine. (Info found here)

  So, my question has been answered. And now, if you made it to the end of this spiel, you are more educated, that when you clicked open my page.  Aren't you glad you visited today?