The US Department for Health and Human Services (HHS) announced last week that it had bought a supply of the drug Nplate from Amgen USA Inc. as part of a "long-standing program" of emergency preparedness using authority and funds provided under the 2004 Project Bioshield Act.
Nplate is designed to treat patients suffering from acute radiation syndrome (ARS), which occurs when a person's entire body is exposed to a high dose of penetrating radiation, reaching internal organs in a matter of seconds, per HHS.
The drug stimulates the body's production of platelets, fighting symptoms of ARS which include uncontrolled and life-threatening bleeding due to a loss of those platelets.
Declining to confirm whether the purchase was linked to escalating rhetoric by Russia, an HHS spokesperson said it was "part of ongoing efforts to prepare for a wide range of threats including chemical, biological, radiological, nuclear, and emerging infectious diseases."
Russian President Vladimir Putin reiterated threats to use nuclear weapons as he announced a partial mobilization of troops in late September.
The US has repeatedly said there is no evidence that Russia is planning to use nuclear weapons against Ukraine or its allies, accusing Putin of "saber-rattling."
But CIA director William Burns said it was "very hard to say" whether Putin was bluffing about using the weapons.
Ukraine President Volodymyr Zelenskyy told the BBC last week that Russia was "preparing their society" for nuclear war, but that "Putin is not ready to do it."
There are fears that Putin could use smaller tactical nuclear weapons in response to the slowing of Russia's progress in its invasion of Ukraine, heightened by a Ukrainian counteroffensive in the last month.
US President Joe Biden said he didn't think Putin was joking when he made those threats, adding he didn't think there was a way to use tactical nuclear weapons and not have it result in "armageddon."
"We have not faced the prospect of armageddon since Kennedy and the Cuban missile crisis," the president said.