should have added that that the vaccine has very limited $$ potential (can't charge a gazillion for it due to bad PR and competition) and most makers have hundred billion brands that can be ruined by this. So they aren't going to risk their company for this. Lastly, suppose Acme Pharma released it against all common sense, all over the media scientists would talk against it, so lose-lose.
This! I have some experience with the big pharma companies and they are risk adverse, even when it comes to PR. They often have billions of dollars coming in from approved products, and they are often more worried about that existing revenue than any potential future revenue.
However, these companies got a lot of money to ramp up production ahead of approval ("at-risk manufacturing") often by governments. If the vaccine is a fluke, they might be in trouble.