That means they expect at least that many gay guys with open sores rubbing up against each other. Ewwwww.
Well, the super spreader event in the Canary Islands (gay pride event also featuring fetish festivals) had an attendance of 80,000, so ...
But seriously, this is a smallpox vaccine, also effective against monkeypox. If they don’t need them, they can be stockpiled for military use (soldiers sent to fight in a conflict are often vaccinated against smallpox in case of biowarfare).