Childhood Vaccines Safe, Review Shows

Dozens of Studies Show Thimerosal, Other Additives Don't Harm Kids

From the WebMD Archives

Dec. 8, 2003 - Parents concerned about the safety of flu shots and other vaccines given to children should be reassured by a newly published review of dozens of scientific studies. A leading pediatric infectious disease expert says the review offers "overwhelming" evidence that the vaccines are both effective and safe.

The pronouncement comes at a time when millions of parents are deciding if they should have their children vaccinated against a flu outbreak, which is hitting children especially hard this season.

The flu vaccine is one of the few immunizations given to children still containing the controversial mercury-derived preservative thimerosal. But vaccine advocate Paul Offit, MD, says there is little reason for worry. Offit is chief of infectious diseases at Children's Hospital of Philadelphia.

"The concerns about thimerosal have centered around its use in children less than 6 months of age, but the flu vaccine is not given to children under 6 months," he tells WebMD. "And the level of thimerosal in the influenza vaccine is very small -- well below the level considered safe for children."

Thimerosal Debate

For more than a decade, antivaccine activists have charged that the thimerosal in childhood vaccines is to blame for a dramatic worldwide rise in the diagnosis of autism. The concerns led to the removal of thimerosal from most childhood vaccines a few years ago. Offit says the action was taken to calm parents' fears, even though there was virtually no scientific evidence supporting the link between vaccines and autism.

Preservatives are used in vaccines to prevent contamination. They were added in the 1920s after children developed severe and sometimes fatal infections after receiving contaminated vaccines.

In his review, published in the December issue of Pediatrics, Offit pooled the studies examining the safety of thimerosal and other vaccine additives, such as aluminum, formaldehyde, gelatin, and egg and yeast proteins.

He says the studies overwhelmingly point to the safety of childhood immunizations, with the exception of rare allergic reactions to the gelatin and egg products used in some vaccines.

"It is no surprise that parents become concerned when they hear that a vaccine contains mercury or aluminum," Offit tells WebMD. "But anyone who lives on the face of the earth is exposed to heavy metals, and the trace amounts used in these vaccines have been shown to be safe. Vaccines are the safest, best tested things that we put into our bodies, and choosing not to have your child vaccinated is not risk free."


Red Wine and Antifreeze

Offit says the type of mercury used in thimerosal, known as ethyl mercury, is far safer than methyl mercury, the most common type of mercury found in the environment. The body eliminates ethyl mercury much more quickly than methyl mercury, with the former having a half-life of about seven days compared with 50 for methyl mercury.

He likens the difference in toxicity between the two to that of the alcohol found in red wine and the methyl alcohol found in antifreeze.

"If you drink [methyl] alcohol you can go blind, but that is not true of wine," he says.

Flu Shots for All?

In light of the flu outbreak, Offit says all parents should consider getting flu shots for their kids. But American Academy of Pediatrics spokeswoman Margaret Rennels, MD, says vaccination probably isn't necessary for all children and could lead to a serious shortage of vaccine. The AAP recommends flu shots for:

  • All children between the ages of 6 and 24 months
  • All family members and close contacts of children under the age of 2 years
  • All children with chronic conditions such as diabetes, asthma, immune disorders, and kidney disorders

"Any parent who wishes to should seek vaccination for their children who don't fall into these categories," say's Rennels, who leads the AAP's committee on infectious diseases. "The vaccine is licensed for all age groups and there are no contraindications."

WebMD Health News


SOURCES: Offit, P. Pediatrics, December 2003; vol 117: pp 1394-1401. Paul A. Offit, MD, chief of infectious diseases, director of the Vaccine Education Center, The Children's Hospital of Philadelphia. Margaret Rennels, MD, chairwoman, American Academy of Pediatrics Committee on Infectious Diseases; professor of pediatrics, University of Maryland.
© 2003 WebMD, Inc. All rights reserved.