Robert F Kennedy believes his voice disease was caused by a reaction to the flu vaccine, according to Joe Rogan.

The podcaster and friend of the new health secretary said Kennedy 'used to take a flu vaccine every year' but 'developed this voice problem... he believes is a vaccine injury.'

Kennedy, 71, suffers from a condition that causes the muscles in the voice box to involuntary spasm, leading to a croaky, strained and shaky voice.

There is no evidence the flu shot can lead to the disorder, spasmodic dysphonia (SD), which is caused by damage to the part of the brain that controls muscle movements.

The condition appears to run in families — Kennedy's sisters, Kerry and Rory, also struggle with vocal issues. 

Kennedy himself has acknowledged there is no proof of a connection between the flu vaccines and SD, he said last year he viewed the shot as 'at least a potential culprit.'

Rogan brought the issue up during his latest podcast episode with actor Woody Harrelson.

Rogan said: 'People dismiss him because his voice is hard, it's hard to listen to sometimes.'

Harrelson replied: 'Yeah that condition he has, you'd think there'd be some way for them to address it, but I don't know.'

Rogan then added: 'He believes that condition came from the flu vaccine. It's a side effect of flu vaccines, he used to take the flu vaccine every year.'

An audibly shocked Harrelson replies: 'Oh. I didn't know that.'

Rogan goes on: 'And so he developed this voice problem and he believes its a vaccine injury, which is very ironic.' 

Harrelson responds. 'Wow. I didn't know that.' 

There have been a small number some reports of people developing voice changes after receiving vaccines.