This isn't professional. Even if he suspected it to be the case -

(which... I could only find two examples https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8349391/ and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8784614/ - the report authors were reluctant to say anything 100% as to causation, but theorised an extremely rare cytokine storm (caused by an extreme immune response))

- it's the kind of theory you need to be careful just floating around due to the amount of misinformation out there. Causation and correlation are different things, and it annoys me when doctors casually say things which could cause further confusion about vaccination.

...Sorry, rant over. Lol <3