In a world of scarce health resources, society would do well to identify major risks to the public's health--and avoid wasting time, money, and expertise on minor ones. Which health interventions are most cost-effective, yielding the greatest gain for the greatest number of people? How much are taxpayers able, and willing, to spend?

Responding to these questions is not easy, given incomplete scientific information and a future that is never truly foreseeable. For guidance in decision making, governments and private-sector entities around the world look to the Harvard School of Public Health and the Harvard Center for Risk Analysis (HCRA). Analyses of health risks by HCRA's faculty have helped shape policies in clinical medicine (in areas such as cancer screening, national guidelines for prevention of disease, and primary health care), global public health (in realms such as antimicrobial resistance, prevention and treatment of AIDS), and environmental regulation (in areas that include food safety, pesticide use, and air pollution controls).

HCRA researchers have gained international recognition for their contributions to health decision science, a field they helped create. This discipline aims to quantify the risks, benefits, and costs of possible courses of action--or inaction--in order to arrive at policies that reduce health risks while taking into account that the cost of bringing them to zero will in most cases be prohibitive. Faculty with expertise in economics, applied mathematics, statistics, and related fields dig deeply into an issue, asking all of the relevant questions and determining all of the known facts. Using quantitative methods and computer models to impose order on the data, they must also factor into their equation another all-important variable: society's values and preferences.
The questions HCRA asks are complex--and the findings controversial, given that our information is often incomplete, and that prioritizing health risks determines how limited resources will be allocated.

Should government impose more stringent regulations on the beef industry to guard against Mad Cow disease, when the risk to the American herd, and the population, is already low?

What are the hazards of mercury in fish? Should Americans limit their consumption of cheap, nutritious tuna and other species rich in omega-3 fatty acids and protein, even if that may mean substituting less healthful foods--including meats high in saturated fat?

Should we pay for cancer screenings on an annual basis, when testing once every two or three years will save billions with only marginal losses in quality-adjusted years of life?

Much as we prefer to act with certainty, reality demands that we settle for probabilities, establishing priorities on the basis of evidence that is conflicting and incomplete. Making informed, reasoned policy is possible, however, through the methodical application of advanced health decision science tools.

No matter the issue, HCRA's mission is the same: First, to quantify and qualify threats to the public's health in objective, unbiased terms; then, to identify interventions most likely to benefit the most people by extending the length and quality of their lives.

Barry R. Bloom
Dean, Harvard School of Public Health