DES MOINES, Iowa - Every year, thousands of American children go through the tearful, teeth-gritting ordeal of getting their vaccinations, only to be forced to do it all over again. The vaccines were duds, ruined by poor refrigeration.

It is more than a source of distress for parent and child. It is a public health threat, because youngsters given understrength vaccines are unprotected against dangerous diseases. And it accounts for a big part of the US$20 million in waste incurred by the federal Vaccines for Children program.

"This is a substantial problem that needs to be addressed through prevention, and when problems are discovered, often times through revaccinations," said Dr. Lance Rodewald, director of immunization services at the Centers for Disease Control and Prevention in Atlanta.

By CDC estimates, hundreds of thousands of doses of vaccines against such diseases as flu, diphtheria, tetanus, whooping cough, polio, mumps, measles, chicken pox and the cervical cancer virus are thrown out each year because of poor refrigeration at clinics, hospitals and doctors' offices.

In one recent case in Sioux City, Iowa, more than 1,000 families were notified by letter and telephone that they needed to get their children revaccinated. State officials found that the refrigerator at the clinic that administered the shots repeatedly dropped below freezing over a 17-month period in 2005 and 2006, potentially ruining the vaccines stored there.

"We just didn't notice it," said Dr. Ray Sturdevant, president of the Prairie Pediatrics and Adolescent Clinic.

Poor refrigeration has been blamed for similar problems elsewhere around the country over the past 2 1/2 years:

  • In St. Cloud, Minn., a clinic had to revaccinate 8,600 patients, most of them children.
  • In Lane County, Ore., 500 children and adults had to get another shot.
  • In western Florida, it happened to about 250 kids.

In Sioux City and other cases, the spoilage resulted from a combination of factors: The refrigerator malfunctioned or was not set or maintained at the proper temperature -- a problem that can be caused simply by leaving the door open for a while -- and the workers responsible for regularly logging the temperature did not seem to recognize when the readings were off.

"We do everything we can to advise and to make people aware that this is very expensive vaccines they're dealing with and we really want to handle it properly and store it properly to prevent these things from happening -- but they do," said Charles Alexander, chief of immunization with the Florida Health Department.

Inadequate refrigeration can cause vaccines to lose their potency, although experts say spoiled childhood vaccines are not dangerous in themselves if given to a youngster.

And there are no known cases of children contracting a disease because they had been given a vaccine rendered ineffective by poor refrigeration. But it could happen, and "that's why we're concerned about it," Rodewald said.