Argument from authority is not particularly strong. The information on putty.org is considered misinformation by the vast majority of professionals in the field of infectious diseases.
This is the modern world that we live in. If being “Vice President and Worldwide Head of Research in allergic and respiratory diseases at Pfizer” with 25 years of career does not qualify to talk about vaccines (in the context of of Covid, I assume because I do not know him or the videos), I frankly don’t know what does
Like being an expert in virology and vaccine therapies for example. Or being boots on the ground rather than a bean counter. Really doesn't take that much imagination now, does it? Or is this "modern world that we live in" this anemic on imagination power?
I'm sure we can then find experts with those kinds of qualifications who also pushed covid misinformation (or to use more old-school terms, straight up fucking lies and unfounded, conspiratorial speculations) and held minority opinions.
Then we can lament on how having a minority opinion means your opinion is definitely being unjustly oppressed, as opposed to justly oppressed, which somehow we'll not be able to produce an example for. Does that really matter though if we can just pretend that we do have an example, or even believe outright we do and just not agree?
Or maybe we can lament on how just blindly trusting either authority or expertise is possibly not the most solid idea in the world. As if we actually had the option to do otherwise at scale, even in the best case scenario, and all people were magically equal and equipped to do so.
Humans and their unattainable reasoning ability. Oh the modern world. Yeah right.
So an expert is exactly the one you want to believe, and no other person, and you tailor the definition just exactly, so only people with your opinion are experts.