The incentives in this case is that doctors will be more likely to fill out VAERS reports, and arguably could fill out unnecessary reports just for the extra cash.
The other incentives regarding vaccines in the medical system I know that you're well aware of: state actors often getting hired by the pharma companies that they're supposed to be regulating, such that their job in - say - the FDA is kind of an interview for future position in pharma; insurance companies giving bonuses to pediatricians who has x% of children fully vaccinated in their practices... it's a long list, but I think you know it well!
