I've heard a lot of arguments that sounded, at first glance, like legitimate concerns. But I haven't seen any that weren't rooted in "People are telling me to be scared so my concern must be legitimate," or "I don't know how this works and it sounds new so I'm worried."

I think people with followings online got a ton of economic benefit from scaring people, the same as the rest of the news industry. Remember Upton Sinclair: "It is difficult to get a man to understand something, when his salary depends on his not understanding it."

The ONE thing I know of that survived study was the higher incidence of myocarditis in young men with Moderna, and provider guidance lists it as a potential side effect. However, the Novavax vaccine had the same myocarditis outcome without being mRNA, and the Pfizer mRNA didn't have that outcome.

It's very unlikely clinical trials would have exposed that issue, so even in hindsight, none of the concerns seem to have been legitimate.