( CNN ) -- `` We will restore science to its rightful place . '' When those words came out of President Obama 's mouth during his inaugural speech , public health nerds such as myself rejoiced heartily . We believe that policy , especially health policy , should be based on scientific evidence . Funny , then , that we ignore this important piece of evidence : When scientific facts go up against moral ideologies , ideology usually wins . I 've worked for more than a decade in the field of HIV prevention . That means working with sex and drugs -- two areas where there is no shortage of good science , and an abundance of ideology . The science tells us , for example , that making clean needles universally available to drug injectors can more or less wipe out HIV transmission in this group . The ideology tells us that providing such services for injectors is tantamount to condoning an illegal behavior that wrecks lives and families and increases crime . If you were running for election , faced with the choice of paying for clean needles and health services for injectors or with putting more cops on the streets and cells in the jails , which do you think would play best with the voters ? Read more about Elizabeth Pisani at TED.com . HIV has taught us something about the nature of democracy as well as the more personal decision-making that my TED talk addresses . The fact is that many of the most effective public health policies have been put in place by governments that Americans think of as ideological , even undemocratic . Iran has one of the world 's better prevention programs inside its jails , and sterile needles are available to injectors from dispensing machines around Tehran . The Kyrgyz Republic gives clean needles to prisoners . China makes needles available to injectors through pharmacies at subsidized prices . These countries are not exactly synonymous with liberalism . Government officials can afford to do nice things for junkies because they do n't need to worry much about what might happen in midterm elections . And they need to be pragmatic because they expect to be in power for some time . Better to put in place prevention programs that deal with a distasteful headache now than to deal with a much greater headache in the future . That 's harder to do in a democracy ; if you do something upsetting to the majority of voters now , you wo n't be around to reap the benefits of your far-sighted action in the future . It 's hardly surprising , then , that for the last 20 years , the U.S. Congress put politically popular ideology ahead of science , denying federal funding for needle exchanges . ( Congress repealed the ban last year . ) At the local level , though , things often look different . Many cities , realizing that they would have to pick up the pieces of the nation 's failed war on drugs , have scraped out their pockets and provided services to injectors . The result has been a huge decline in new HIV infections among drug users and their sex partners ; the burden on the health system has of course fallen , too . And there is no evidence at all that these programs have led to a rise in injecting -- a specter commonly raised by the ideologues . The truth is , people who 've never injected drugs in their life do n't suddenly say : `` Oh look , a clean needle dispenser . Maybe I 'll try shooting up heroin . '' This disconnect between national and local policies is instructive about the way democracy works . At a national level , politicians seem to respond to what they think the electorate wants to hear . Ideology and rhetoric rule . At the local level , however , they are more likely to respond to what the electorate really needs -- workable solutions to real problems . The only workable solutions are the ones that are based on good , solid , scientific evidence . In my little corner of public health , the Obama administration is following through on its promise to put the science back into policy . Since the ban on federal funding for safe injecting programs was dropped in December , the sky has not fallen , and if the government falls , it certainly wo n't be because of this small piece of pragmatism . But two decades of banging the `` evidence-based '' drum does make me think that we scientists need to learn from the evidence . Scientifically sound solutions can only be implemented where they can be made politically workable . The opinions expressed in this commentary are solely those of Elizabeth Pisani .
Elizabeth Pisani says Obama 's embrace of science in setting health policy is encouraging . But political and moral ideology , she says , often wars with science-based policy . Data show that giving drug users clean needles stalls HIV 's spread , she says . Pisani : Science-based solutions must be made politically workable to be implemented .