Last month, a 27-year-old woman with a case of measles she picked up in London exposed hundreds as she flew into the Washington area and then on to Denver and Albuquerque, N.M. She had never been vaccinated for the disease.

The woman who spread the measles isn't an outlier. Rather, she's the product of a zealous and largely unchecked movement to convince parents that vaccinations can harm their children.

"Virtually every single empirical claim of vaccine rejectionism is factually false," notes Dr. Amy Tuteur, an obstetrician-gynecologist and blogger, "but parents who lack even the most basic understanding of immunology are often incapable of evaluating those empirical claims. Indeed, those parents most likely to proclaim themselves 'educated' on the topic are generally the most ignorant."

But many parents - most of them white, affluent mothers - believe otherwise, and not by accident. Making vaccines sound scarier than measles and the other infectious diseases they prevent took a village of anti-vaccine organizations fomenting fear.

One prominent proponent of the idea that vaccines cause autism and brain damage is Andrew Wakefield, who began using the Web and other media to promote his "research" on the subject in the 1990s. Wakefield's findings were discredited, but not before they sparked a growing anti-vaccination movement. Its members theorize that the government, the pharmaceutical industry, and the medical community have conspired to hide the dangers of vaccines in an effort to protect corporate profits.

The media have been part of the problem. Rather than exposing fraudulent claims, sympathetic reporters have fueled anti-vaccine groups, spread panic, and crowned celebrities such as Jenny McCarthy as immunization experts. Meanwhile, they have depicted true leaders in the field, such as Dr. Paul Offit of the Children's Hospital of Philadelphia, as less reliable because of their connections to commercially successful vaccines.

As they plug their books, diets, and supplements, McCarthy and others have flogged the message that the best defenses against childhood disease are conspicuously "natural" - including prolonged breast-feeding and exposure to other sick children at measles and chicken pox "parties." That's right: The supposedly enlightened anti-vaccine parent protects her kids by exposing them to diseases that have killed millions.

It would be nice if our public officials stood up to these fearmongers instead of treating them as just another interest group. But apparently that's too much to ask of the Obama administration, which seems to have gone out of its way to legitimize the belief that vaccines cause autism.

In 2009, the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices postponed the release of the swine-flu vaccine because of safety concerns raised by McCarthy's group, Generation Rescue. Now the CDC committee - which makes far-reaching recommendations about what vaccinations America's children should receive - appears to be backing away from a lifesaving infant vaccine to prevent meningococcal disease, a leading cause of bacterial meningitis.

That's despite the fact that in 1999, meningococcal disease was on the CDC's list of 10 conditions targeted for elimination. And the CDC voiced its support for an infant meningococcal vaccine in 2008, citing data that demonstrated its safety and potential to greatly reduce harm caused by the disease.

Last year, however, Obama's CDC showed signs of backing down from that position. The immunization committee indicated that it might not recommend the vaccine for infants. Among the reasons it cited was the potential for a "rare adverse event."

Last month, the Obama administration released its long-awaited National Vaccine Plan, which devoted a lot of attention to overcoming cultural and economic barriers to immunization. But it didn't include a word about bogus claims that vaccines are dangerous. And then Environmental Protection Agency chief Lisa Jackson joined the panic parade by suggesting that contaminated drinking water causes autism.

Wakefield helped launch a powerful movement against immunizations. Sadly, the Obama administration has been unable or unwilling to generate a strong provaccine response.

If measles and other diseases continue to surge, we can't just blame those who spread them. We can also thank the politicians and health officials who fail to protect us from deadly diseases and lethal stupidity.