Some of this is just general knowledge that I've picked up here and there but when I want to point people to stuff I tend to use-

Short overview of FDA trials and what each phase means and remind them we are in Phase 4 meaning the drug is available for use but they monitor it heavily for any additional side effects or other issues.

Normally when you submit a vaccine to the FDA your on a waiting list and you're behind everyone else who put one in before you. They bumped everything related to covid to the front of the line (which is why test options got quick approval too) and they cut out arbitrary waiting periods between trials. This source is good or if you want a short blurb about how they basically sped up paperwork there is this as well

mRNA vaccines are new and really cool but also rely on known science so they are pretty safe. Bonus source

Here's something about people with egg allergies reacting to current vaccines this does not apply for all vaccines but its useful to mention whenever people bring up allergic reactions to this vaccine (which tbf does not contain eggs or gelatin, the two common causes of allergic reactions to vaccines)

Sorry that this is kinda surface level info/articles, if someone has a comphresive source on all this I'd love it so I can send it to people lol. Please re-evaluate the vaccine discussion here because it's outright dangerous. People possibly declining this vaccine puts them and everyone around them at risk