The attack was retaliation for a US drone strike in Baghdad on Jan. 3 that killed top Iranian General Qassem Soleimani.
President Donald Trump and the US military had said there were no casualties after the strike on the Ain al-Asad airbase in western Iraq.
"I'm pleased to inform you the American people should be extremely grateful and happy," Trump said on Jan. 8 in a live address to the nation. "No Americans were harmed in last night's attack by Iran."
“While no US service members were killed in the Jan. 8 Iranian attacks on Al Asad airbase, several were treated for concussion symptoms from the blast and are still being assessed,” Captain Bill Urban, spokesman for US Central Command, said in a statement, AP reported.
"As a standard procedure, all personnel in the vicinity of a blast are screened for traumatic brain injury, and if deemed appropriate are transported to a higher level of care,” he added.
"When deemed fit for duty, the service members are expected to return to Iraq following screening," Urban said. "The health and welfare of our personnel is a top priority and we will not discuss any individual's medical status."