A new specter haunts U.S. health care: a potential shortage of childhood and other life-saving vaccines.

In recent years, vaccine supplies have become an ongoing concern for U.S. health officials, doctors, and parents. From 2000 to 2003, the U.S. suffered a severe shortage in children’s vaccines.

Forty-nine states were forced to implement rationing programs for commonplace, but critical, vaccines for the mumps, measles and rubella.

In all, an estimated eight out of 11 vaccines for preventable diseases were not being produced in sufficient quantities to immunize American children.

Elected officials were rightly worried that the shortage would have caused a public health crisis had there been an outbreak of even routine childhood diseases.

In 2001, Democratic Rep. Peter DeFazio of Oregon introduced legislation that would have allowed the government to declare a “public health emergency” based on vaccine shortages and then seize vaccines from pharmaceuticals.

DeFazio asserted that it had become clear that a “market driven system for delivering vaccine doesn’t work when there’s a shortage or outbreak.” DeFazio was correct to emphasize the risks of a vaccine shortage, but his targeting of the free market was off base.

Ironically, the government’s own intervention sparked the sudden shortage. The Food and Drug Administration, which needlessly inhibited the vaccine supply, was at the heart of the problem.

One mistake was the FDA’s sudden decision in 1999 to ban all use of thimerosal in child vaccines. Thimerosal is necessary for preserving vaccines and has been used in the U.S. (and around the world) for decades. Although no study has ever found any ill effects associated with thimerosal, the FDA decided to ban the substance because it contains trace elements of ethyl mercury.

The American Academy of Pediatrics hesitantly supported the ban, provided it didn’t reduce the number of child vaccinations—a danger the AAP found far outweighed any unknown potential risk of thimerosal.

The effects of the new requirements were too drastic for many pharmaceutical companies. Aventis Pasteur had to switch production of DTaP, a vaccine for diphtheria, tetanus, and pertussis (whooping cough) given primarily to babies, from multidose vials to tiny single shot vials to eliminate thimerosal but maintain the vaccine’s shelf life.

The new requirement cost Aventis two years of development effort but also decreased the company’s vaccine production capability by 25%. Another pharmaceutical maker, Wyeth, was unable to meet the thimerosal requirements, contributing to its decision to stop producing DTaP altogether.

The decision of even one company to stop making a particular vaccine can spark a crisis. Wyeth’s exit from the DTaP market had large repercussions because the company produced about a third of the nation’s DTaP supply.

That case would not be an exception. There are only four pharmaceutical companies that provide nearly all of the childhood vaccines used in the U.S.—Merck (U.S.), Wyeth Pharmaceuticals (U.S.), Aventis Pasteur (France) and GlaxoSmithKline (United Kingdom).

With so few companies producing vaccines, the U.S. is highly susceptible to sudden vaccine shortages and equally sudden price spikes. Instead of encouraging new companies to enter the vaccine market, the FDA’s expensive and time consuming approval process—as well as its cumbersome manufacturing regulations—discourages new companies from making vaccines and may even further decrease the total number of vaccine producers.

Barely 100 years ago, more than one in 10 American infants died from vaccine-preventable diseases. Since the introduction of vaccines, the incidence of these diseases has dropped by 99%.

Under present law, the FDA is responsible for ensuring that these vaccines are effective and safe. But the FDA has an equal responsibility to ensure that it does not hinder the market’s ability to deliver enough vaccines to protect every American child in need.