[frud]

That's quite an injection if it can cure six children at once.

[thfuran]

It must have been a pretty terrifying needle.

[inglor_cz]

That's nothing, one small kid with one remaining cowpox lesion was the source of vaccination material for Spanish America.

https://en.wikipedia.org/wiki/Balmis_Expedition

(They took off from Europe with 22 kids and did an "infectious relay" in pairs. By the time they got to South American mainland, precisely 21 kids already resolved their cowpox. One last kid was still barely infectious, thus becoming the sole source of the vaccination material.)