Key word: known. The Soviet bioweapons program was about four orders of magnitude larger than anything the US knew about and it took up a small office complex that would fit in a conventional business park without notice. It was visited and inspected and the West found fuckall, despite the fact that there were twenty metric tons of weaponized smallpox and the warheads to launch it on site. Smallpox has long been a preferred biowar agent because the US was one of the first countries to stop vaccinating. And if you think the DoD isn't well aware of this... https://en.wikipedia.org/wiki/Smallpox_vaccine I'm generally a level-headed individual but no lie - I spent a few days trying to line up a smallpox vaccination after 9/11 and it's one that can kill you. While biological warfare has been practiced only sparsely, smallpox is such an obvious vector that blindly throwing up your hands and saying "I'm sure everybody will comply with this!" is naïveté of the first order.Responding to international pressures, in 1991 the Soviet government allowed a joint US-British inspection team to tour four of its main weapons facilities at Biopreparat. The inspectors were met with evasion and denials from the Soviet scientists, and were eventually ordered out of the facility. In 1992 Soviet defector Ken Alibek confirmed that the Soviet bioweapons program at Zagorsk had produced a large stockpile—as much as twenty tons—of weaponized smallpox (possibly engineered to resist vaccines), along with refrigerated warheads to deliver it. It is not known whether these stockpiles still exist in Russia. In 1997, however, the Russian government announced that all of its remaining smallpox samples would be moved to the Vector Institute in Koltsovo.9 With the breakup of the Soviet Union and unemployment of many of the weapons program’s scientists, there is concern that smallpox and the expertise to weaponize it may have become available to other governments or terrorist groups who might wish to use virus as means of biological warfare.
Starting in early 2003, the United States government quietly started vaccinating 500,000 volunteer health care professionals, throughout the country. Vaccinees were healthcare workers in emergency departments, intensive care units, anesthesiologists, and health care workers in other settings who would be crucial first-line responders in the event of a bioterrorist attack using smallpox. Many healthcare workers refused, worried about vaccine side effects, but many others volunteered. It is unclear how many actually received the vaccine. In 2002, the Israeli army, in a similar attempt at mass vaccination, found many soldiers unwilling to volunteer.