October 22, 2004

Flu vaccine being studied in infants under 6 months old

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Monique and William Greer, parents of William Jr., listen carefully to Alice O’Shea, a clinical research specialist. Researchers at Vanderbilt are recruiting infants for a study about flu shots for infants under the age of 6 months old. (photo by Dana Johnson)

Flu vaccine being studied in infants under 6 months old

Beginning this year, the Centers for Disease Control is recommending children 6 to 23 months old be vaccinated against influenza because they are considered a high-risk group.

But what about those under 6 months old?

That’s a question that researchers at the Monroe Carell Jr. Children’s Hospital at Vanderbilt want to answer.

Natasha Halasa, M.D., is now seeking participants for a study administering the influenza vaccine Fluzone to infants 10 to 22 weeks old. Currently, the vaccine is not licensed for use in children younger than 6 months old.

“These infants are part of vulnerable group and have high hospitalization rates for influenza-related illnesses that are similar to the elderly,” said Halasa, assistant professor of Pediatrics in the division of Infectious Diseases.

As part of a National Institutes of Health-funded study, Halasa and Kathryn Edwards, M.D., professor of Pediatrics and vice chair for Clinical Research in the department, has begun to vaccinate the 50 infants with two doses of the flu vaccine, as recommended for all children who are immunized against influenza for the first time.

The infants will then be monitored to determine if the vaccine is effective in protecting against flu and its complications, and whether it is safe. The flu vaccine that is being given is the thimerosol-free pediatric dose. This is the same vaccine that is already approved for use in children 6 months and older.

“There are some people who are concerned about thimerosol in vaccines and others who are concerned about vaccines in general,” Halasa said. “But the risks associated with the flu are far greater than the risks associated with the flu vaccine. Influenza vaccine has been tested in a small group of high risk babies younger than 6 months and the side effects that were reported were minor with the first dose and none reported with the second dose.”

While the idea that young children are severely affected by the flu may be new to parents, researchers at the Children’s Hospital have been reporting the risk in the youngest children for years.

Research over the last four years, some of it done at Vanderbilt using medical records from the state’s TennCare database, proved that infants less than 6 months are more likely than other children to be hospitalized with complications of the flu.

Complications of influenza can include pneumonia, dehydration, worsening of long-term medical problems like heart disease or asthma, swelling of the tissues of the brain, and other bacterial infections, including sinus and ear infections. In some cases, these complications can be very severe.

News of the flu shot shortage may make recruitment easier for Halasa and her staff. Already, parents are showing interest simply because of all the media attention about the shortage of the vaccine, she said.

For more information about the infant influenza vaccine study, call Alice O’Shea at 343-8518.