This is strange
US stock of vaccine is ~ 180 million doses already, up from ~ 20 million in 2001.
That's $2.5 billion spending - why? The threat is large, but live virus is almost impossible to get.
New Zealand, Canada and various European countries are also all moving to acquire very large vaccine stockpiles, basically for 100% population coverage; far more than needed to firewall any plausible point breakout.