September 3, 2008
A Vaccine Safety Expert Replies
With record rates of immunizations in the U.S., the vaccines themselves are now under scrutiny by a small but vocal segment of the population. Concerned that the vaccines may pose greater risks than the diseases against which they protect, some parents are refusing them. So, in addition to developing new vaccines – Johns Hopkins researchers like Hopkins Children's pediatrician Neal Halsey are employing Johns Hopkins rigidly scientific approach to studying vaccines and any adverse effects.
“Some parents, and even clinicians, today are apprehensive,” says Halsey. “There are many rumors. We are looking at all the safety issues as they crop up and generating the scientific data to make policy.”
Halsey is director of the Institute for Vaccine Safety at the Johns Hopkins Bloomberg School of Public Health, which coordinated the scientific review of concerns, raised about a possible link between childhood diabetes and vaccines and found no evidence to support the hypothesis. When there was public concern in the late 1990s, however, that a preservative, thimerosal, that was used in some vaccines, could result in exposures that exceeded EPA guidelines for exposure to a related form of mercury, Halsey led a review for the Academy of Pediatrics in 1999 that recommended, as a precaution, thimerosol levels be reduced or removed from vaccines given to infants, and it was. Subsequent studies have not shown consistent evidence of harmful effects other than rare allergic reactions.
Some families of children with autism believed that thimerosal might have caused autism, but numerous scientific studies conducted in the past 10 years have shown that thimerosal does not cause autism. Other families and one gastroenterologist falsely believed and promoted the idea that MMR might cause autism.
Ironically, Halsey says, “the MMR vaccine can prevent the very infection, rubella, that science does link to autism. When rubella infects a pregnant woman, the unborn child gets infected and often suffers severe neurologic damage, including autism in some children. Just as people should not be misled by promises of cures from fake medicine, we should not mislead people with false villains to blame when unexpected illness occurs.”
Recognizing the potential of vaccines, like all drugs, to cause allergic reactions, Halsey and Hopkins Children’s chief of immunology, Robert Wood, joined forces and coordinated the development of guidelines with other vaccine and allergy specialists to help clinicians evaluate and provide vaccines for children and adults with suspected hypersensitivity to vaccines. Their guidelines appear in the September 2008 issue of Pediatrics.
“Our ultimate goal in all of this at Hopkins,” says Halsey “is to help make sure we use the safest vaccines possible and maintain parents’ confidence in them.”
Delaying or refusing vaccinations for children leaves them vulnerable to contagion and spreading disease to others at risk, he says, adding: “This is not a lesson we need to learn again.
“The CDC recently announced that we have had more cases of measles in the United States this year than in any year in the past decade. Many of the children who developed measles had not been vaccinated because of false concerns about vaccine safety.”