When you get a PhD in microbiology then you can consider yourself informed on vaccine science. Until then, you're not.
Ok so let me try to break it down.
This isn't just an Appeal to Authority argument, it's a bad one.
In order to make such an argument and have it stick, you first have to have both sides in the debate agree what constitutes an authority. So even if you had picked a field specifically related to vaccines, you would need for us to agree that
1) such a field does actually constitute expertise,
2) that the person holding said degree holds it validly,
3) that the degree came from a reputable source,
4) that this person's knowledge is current (and not reflective of a degree awarded in 1968 or so),
et cetera.
You didn't even get to step 1. You said "PhD in Microbiology".
So according to what you wrote, if I had a PhD in Microbiology and was a practicing mycologist specifically studying Ophiocordyceps unilateralis and potentially adapting it for use in the fight against fire ant spread in the Southern US, you would accept those credentials in the vaccine debate.