The only meaningful danger from rushing the vaccine into development was that it would be ineffective, not that it would be dangerous. Vaccine technology is well-advanced enough, and the method tested thoroughly enough, that there were no reasons to expect any excess health risks.
An ineffective vaccine would still be a problem -- the longer we went without a means of combatting this disease, the worse it would be. But it wouldn't be in itself a danger (and, of course, an ineffective vaccine wouldn't be made available for wide distribution, so would anyway not be a danger to the wider public).