Resident Fellow  Scott Gottlieb, M.D.

Measles, which once killed 500 American children a year, is making a comeback--and some New York lawmakers are eager to help the disease prosper.

The Centers for Disease Control reports a surge in measles outbreaks; almost all the cases are in children who never received the routine shots for measles, mumps and rubella (MMR). Vanquished diseases are rebounding thanks to growing--but groundless--fears over the safety of traditional vaccines.

Driven by those fears, ever more parents are finding a way to forgo shots for their children--even though shots are required in most of the nation.

And some politicians are encouraging them. A proposed New York law, sponsored by Suffolk County Assemblyman Marc Alessi, would establish a "philosophical" exemption to mandatory childhood vaccinations.

Like many other states, New York has long allowed religious or medical exemptions, but this "philosophical" pass would let parents skip mandatory vaccines for their kids for almost any reason, just by filling out some paperwork.

The political hysteria comes from speculation tying thimerosal, a mercury-containing preservative in vaccines, to autism. In fact, the substance has been largely phased out of most shots, and exhaustive research has debunked the idea that it's linked to neurological problems.

The consequences of autism can be devastating, and the rise in the condition's incidence is of great concern. Yet too many people still cling to a few flawed ideas about its origin--none more prominent than the purported link to thimerosal.

Data on the issue has been reviewed in high-profile, public forums, including: the National Vaccine Advisory Committee, two recent meetings of the Advisory Committee on Immunization Practices of the CDC and the Institute of Medicine's Immunization Safety Review Committee.

Through its Vaccine Safety tracking system, the CDC has examined the incidence of autism as a function of the amount of thimerosal a child received from vaccines. The results of these and other reviews conclusively show that there's absolutely no causal link between autism rates and the amount of thimerosal children received.

In July 1999, the Public Health Service agencies, the American Academy of Pediatrics and vaccine manufacturers agreed that thimerosal should be reduced or eliminated in vaccines as a precautionary measure and to help ensure public confidence. And, since 2001, thimerosal has been removed from or reduced to trace amounts in all vaccines routinely recommended for children 6 and younger (with the exception of inactivated influenza vaccine).

A recent study of more than 30,000 Japanese children in Yokohama provides still more evidence nixing the thimerosol connection. Use of the MMR vaccine was briefly suspended there after reports that a manufacturing problem led the anti-mumps component of the vaccine to cause meningitis--yet the number of children with autism continued to rise. Before withdrawal of the vaccine, there were up to 86 cases of autism reported per 10,000 Japanese children; after the kids stopped getting the MMR shots, there were as many as 161 cases per 10,000.

As a culture, we have a troubling propensity to allow science to validate populist theories, but not to exclude them.

Our trust in the scientific process seems to be a one-way proposition.

When it comes to vaccines, safety concerns have always been paramount--for these products are given to millions of otherwise healthy children.

Any safety problems could have devastating consequences.

For these reasons, and many others, vaccines are among the most closely scrutinized and carefully regulated health-care products on the market. But that reality, and reams of the scientific evidence, isn't enough to quell fears.

The result is 64 new cases of measles since January, according to the CDC--more than in all of 2006 and the highest number since 2001. The largest outbreak, 22 cases so far, is under way right here in New York, mostly in the Borough Park section of Brooklyn.

Before 1963, when the vaccine became available, America saw 3 million to 5 million cases of measles a year, killing as many as 500 children a year and putting 48,000 in the hospital. The vaccine wiped out transmission by 2000, but measles can still be imported from countries where its incidence is widespread. (The Brooklyn strain was probably introduced by immigrants.)

Worldwide, measles kills about 242,000 children a year.

The recent outbreaks should be a warning to politicians here in New York, as well as those in 18 other states that have already passed loose vaccine exemptions. There's nothing "philosophical" about stoking a modern outbreak for the sake of some careless political pandering.

Scott Gottlieb, M.D., is a resident fellow at AEI.