One thing ACA did which at least is plausibly useful (though whether it'll move any statistics remains to be seen) is to include an annual physical plus all CDC-recommended vaccines with $0 billed-to-patient cost. So even if you otherwise have a high-deductible plan, you don't pay a copay or deductible for those services. This isn't quite an active incentive, but it's an attempt to remove the price disincentive, with the hope that'll result in higher vaccination rates (the flu vaccine is included).
