The Federal Government
https://www.wired.com/story/us-postal-plan-coronavirus-vaccine-doomsday/
https://www.gao.gov/products/gao-09-59r
Sec. 3. Federal Rapid Response. (a) The Federal Government must develop the capacity to anticipate and immediately supplement the capabilities of affected jurisdictions to rapidly distribute medical countermeasures following a biological attack. Implementation of a Federal strategy to rapidly dispense medical countermeasures requires establishment of a Federal rapid response capability.
https://obamawhitehouse.archives.gov/the-press-office/executive-order-medical-countermeasures-following-a-biological-attack