Health and Human Services Secretary Kathleen Sebelius' decision this week to overrule the Food and Drug Administration commissioner and refuse to authorize girls under age 17 to have over-the-counter access to the emergency contraceptive pill known as Plan B is exactly the kind of triumph of politics over science that one might expect of the last administration.

But even under President George W. Bush, there was a grudging acknowledgment that the "morning-after" pill ought to be available to women without a prescription. The scientific evidence was simply too massive too ignore. And so, after the Bush administration initially refused to authorize over-the-counter access, officials eventually agreed to a compromise in 2006 that made Plan B available without a prescription to women 18 and older (with the cut-off lowered to age 17 in 2009 as part of a court-ordered review).

The argument against providing greater access to girls 16 and under was never regarded as strong, and the HHS secretary's suggestion Wednesday that there's been insufficient study of the effects on 11-year-olds is laughable. Drugs with far greater risk — acetaminophen, for instance — have been made available to children with far less research on pre-teen use.

But here's what is known for certain: Plan B is most effective at preventing pregnancy when it is taken as soon after unprotected sex as possible. Obligating a woman to seek out a doctor and get a prescription only raises the risk of unintended pregnancy.

This is not some rarely used or potentially risky drug formulation capable of disrupting an existing pregnancy. First made available in this country in 1999, Plan B uses the same hormones found in ordinary birth-control pills to prevent pregnancy. It should not be confused with RU-486 or mifepristone, the drug that is used to terminate pregnancy and is only administered at clinics or doctor's offices.

Nor can it be argued that young girls are incapable of understanding the consequences of the drug or that they are unlikely to use it properly. Studies show access to the drug does not increase sexual activity and doesn't lead to health-threatening overuse.

This much is also clear: Social conservatives and some religious groups oppose making Plan B more widely available — much as people have opposed other forms of birth control on moral grounds. Some believe life begins before a women's egg is implanted in the wall of the uterus and that the drug's potential interference with that process amounts to a form of abortion. But public health decisions should not be based on religious faith or appeasing those with political influence. They should be made by looking out for the health and safety of all.

Never before has an FDA commissioner been overruled in such a manner. The agency's decision was based on the expertise of pediatricians and obstetricians, advisory panels and studies compiled by the drug's manufacturer. In other words, it was the best medical advice available.

In his inaugural address, President Barack Obama pledged to "restore science to its rightful place." By that, he appears to mean he'll support science when it's convenient but not when it might rally social conservatives against him. But if a Democratic president can't stand behind the medical findings of the FDA, who will?

Unfortunately lost in this decision is the welfare of the teens affected and the prospect of more unintended pregnancies. That is likely to lead to more abortions — a circumstance conservatives claim not to want. Estimated to number 1.6 million per year in the U.S., unintended pregnancies are a serious and costly problem that contribute to the cycle of poverty and the incidence of birth defects.

That's not to suggest that Plan B should be regarded as anything more than a back-up method of birth control, one that does nothing to reduce the risk of sexually transmitted disease. But medically unnecessary restrictions on access to birth control are unfair to women, a point that should have been obvious to Ms. Sibelius, who has generally been viewed as a champion of women's health care rights and as staunchly pro-choice.

Perhaps Mr. Obama felt an obligation to balance some of his more progressive policies (insisting contraceptives be funded under health insurance reform, for instance). But how disappointing that he would make that political calculation at the expense of teen girls who, instead of the bogus threat of a commonly used drug, must face the very real health threat of unwanted pregnancy.