Don't be ashamed about vaccine shopping.

There are very good reasons to do so - for example, if there was a some evidence that Pfizer would have supply issues (compared to, for example, Moderna) this could impact your second dose (availability and efficacy). People here are very quick to judge and pontificate. I feel especially bad for that one girl who posted here with a serious clotting disorder who has concerns about AZ - instead of suggesting she talk to a doctor, people harassed her and shamed her for "vaccine shopping". The only thing worse than a bad person is a bad person who thinks they're a good person.

There's nothing wrong with watching out for yourself - especially if you're immunocompromised. I suppose one piece of advice is don't accept any significant delays due to shopping. 1 dose now with mixing is probably better than matched doses much later.