President Joe Biden is asking states and localities to offer unvaccinated residents $100 to get their COVID-19 shots.

The cash reward for vaccination was one idea in Biden’s latest plan to boost lagging vaccination rates in many parts of the nation. Rolled out Thursday, the core of his new plan is a requirement for federal workers to disclose their vaccination status to their agencies.

Biden is pointing to anecdotal evidence that a $100 reward will get results. The White House says the Kroger grocery store chain tried it and saw vaccination rates jump to 75% from 50% among employees. New Mexico, Ohio and Colorado have also experimented with the idea.