WASHINGTON – Health and Human Services Secretary Robert F. Kennedy Jr. told USA TODAY he stopped taking flu shots in 2005 because of his concerns about side effects, including suspicions about what damaged his voice.

Kennedy, 71, said he got annual flu shots through the mid-1990s. But he said he gave them up for good in 2005 as he became more aware of possible side effects.

Kennedy’s speech often sounds strained and broken from a condition called spasmodic dysphonia, also called laryngeal dystonia. He said he couldn’t prove a flu vaccine caused his condition, but that it was one potential reason.

“That’s why my voice is so screwed up,” Kennedy said Jan. 16 in an exclusive interview for the USA TODAY series "Extremely Normal." “Do I know whether that was caused by my annual flu shot? I have no idea. It’s a possibility. It’s a potential culprit that I cannot rule out. I can’t prove it.”

The Dystonia Medical Research Foundation has said vaccines don't cause the condition and can actually protect against some forms of dystonia.