That 300m seems very excessive to me as well. Unless they are assuming it's a flu like thing where they'll need to vaccinate every year? Just speculating.
I can’t imagine they believe that the vaccine they purchased will be used next year as part of an annual thing. I do think it will be an annual shot like the flu, but also like the flu, I think everyone realizes that the vaccine will need to be constantly updated to account for variants. This year’s vaccine may be worthless by next December if the virus keeps mutating like it appears to be doing.