There's way too much pressure for the government to release a vaccine and then have it cause major side-effects, so I don't think we should be worried,
however since Trump was told to wait with releasing the vaccine until after the elections, they might be worried of it coming with side-effects as well.
To provide a 100% safe vaccine is the government's and the citizen's 1st priority. Why? Because if every person with the vaccine suddenly needs emergency help - due to side-effects, then covid19 would just take another huge bite into USA's wallet, so they are most likely not releasing this vaccine, half-assed.
I trust the modern medicin engineering, so I'll take it anyway.