Preventive medical care includes services such as cancer screening, cholesterol management, and vaccines. In making its estimates of the budgetary effects of expanded governmental support for such care, CBO takes into account any estimated savings to the government that would result from greater use of preventive care as well as the estimated costs of that additional care. Although different types of preventive care have different effects on spending, the evidence suggests that for most preventive services, expanded utilization leads to higher, not lower, medical spending overall.
That result may seem counterintuitive. For example, many observers point to cases in which a simple medical test, if given early enough, can reveal a condition that is treatable at a fraction of the cost of treating that same illness after it has progressed. But when analyzing the effects of preventive care on total spending for health care, it is important to recognize that doctors do not know beforehand which patients are going to develop costly illnesses. To avert one case of acute illness, it is usually necessary to provide preventive care to many patients, most of whom would not have suffered that illness anyway. Judging the overall effect on medical spending requires analysts to calculate not just the savings from the relatively few individuals who would avoid more expensive treatment later, but also the costs of the many who would make greater use of preventive care.
Of course, just because a preventive service adds to total spending does not mean that it is a bad investment. Experts have concluded that a large fraction of preventive care adds to spending but should be deemed “cost-effective,” meaning that it provides clinical benefits that justify those added costs.
CBO Director Elmendorf's blog post on prevention and wellness costs
CBO response to Congressional questions about possible cost savings from prevention