From: "The Last Vial"

"It's a lovely plan. Yes, lovely, if it weren't so horrible in its implications. He paused to drain his cup. 'For the past several years there has been very strong emphasis on public health measures in the USSR. A tremendous drive for vaccination against polio, small pox and various other communicable diseases has resulted in the immunization of millions of children and adults. I'll bet if we could get some of those vaccines we'd find the antidote to both our flu virus and the Chinese small pox-measles, whatever it is. I think there has been deliberate selection of part of the population to carry on the Soviet system and the rest will be sacrificed just to fool us.'

1960.