Virginia Postrel says:
Speaking of immigrants, I can’t help wondering whether the estimates of how many (or rather, how few) Americans have been vaccinated against smallpox fully account for the immigrant population. I’ve noticed quite a few vaccination scars on the upper arms of relatively young Vietnamese manicurists.
Jay Manifold says vaccinations are good for 50 years, but I’d rather not bet my life on that estimate. My last vaccination was in 1966, as a requirement for entering first grade, but it “didn’t take” because I still had immunity from my vaccination in infancy. See how common these things used to be?
I imagine most immigrants from the developing world were vaccinated at least in the 1970s. Both my wife and I were vaccinated against smallpox when we were kids and have the scars to show for it.
UPDATE: The last case of smallpox infection in Pakistan was in 1974 while the last case worldwide was in 1977 in Somalia.