Yesterday, I had to take a tuberculosis skin test for work. A truly foreign concept for Brits, who receive a Bacillus Calmette-Guérin (better known as a BCG) vaccine in childhood and then are done with it.

Now most Americans have no idea that a vaccine exists for tuberculosis. I know I didn’t. I thought it was a joke when I studied in Scotland and found that everyone had this weird pox scar on their upper arm, a scar left over from the vaccine. Apparently the shot hurts like hell when you get it. I mean, pox-scarring, hold-on-don’t-pass-out pain. But it means immunity for life. Well, almost.

Apparently, the efficacy of the shot actually depends on your geography. Whaaaa? Yes, apparently UK trials have shown a 60-80% protective rate, but the closer you get to the equator, the less effective the shot. And there are scientific reasons for that, but I won’t bore you.

What I will say is that it does sort of explain why American doctors, who are typically vaccine-crazy, don’t give out the BCG vaccine. Only these TB skin tests, which can be given on a regular basis to check for exposure to TB.

We have dodged the big needle, my friends. Sometimes, being American has its privileges.