Study Questions Guidelines on Immunizations

Researchers suggest needles used on kids are sometimes too long

Randy Dotinga

Randy Dotinga

Published on October 03, 2008

FRIDAY, Oct. 3, 2008 (HealthDay News) -- New research suggests that federal guidelines on the length of needles used to vaccinate children could put some kids in danger of injury.

"Based on our findings, the CDC [U.S. Centers for Disease Control and Prevention] should alter their guidelines," said study author William C. Lippert, a graduate student at Tulane University School of Public Health and Tropical Medicine.

However, a Vanderbilt University pediatrician questioned whether new guidelines calling for shorter needles are needed, since the nurses he works with rarely experience problems with immunizations.

Childhood vaccines are typically given through intramuscular injections, often in the thigh (for young babies) or in the shoulder (for older children). The injections "deposit" the vaccine in the muscle, Lippert said.

"These injections are given this way to keep irritation and inflammation at a minimum," Lippert said. "Studies have also shown that these types of injections are more readily absorbed by the body and produce a better immune response."

It's important to make sure that the size of the needle is appropriate for individual kids, Lippert said. "The problem is that if the thickness of the needle becomes too small, the needle doesn't penetrate the skin as well and tends to bend. This bending will sometimes cause the needle to break."

Overpenetration is another problem, although it doesn't get as much attention, the study authors wrote. If the needle travels too far into the body, it can strike bone or break off from the syringe.

In the new study, published in the September issue of Pediatrics, researchers used MRI and CT scans to study the thickness of fat tissue and muscle layers in 250 children aged 2 months to 18 years.

They reported that federal recommendations about the lengths of needles don't take into account the bodies of children. Nearly four in 10 babies under the age of 1 would suffer from overpenetration of needles if they got injections in the thigh with the size needles that are typically recommended, the study said. One-inch needles are also recommended, and they'd cause overpenetration 11 percent of the time, according to the study.

Patients who got vaccinated in the shoulder with 1-inch needles would have overpenetration 61 percent of the time, the study reported. For two other recommended needle lengths, 5/8-inch and 7/8-inch, the rates of overpenetration were estimated at 11 percent and 55 percent, respectively.

The study authors recommended that the guidelines be changed to support the use of shorter needles in many cases, depending on the gender and weight of the child.

Dr. Joseph Gigante, an associate professor of pediatrics at Monroe Carell Jr. Children's Hospital at Vanderbilt, spoke to five nurses, and they all reported that "it's incredibly uncommon to have problems associated with the injections," he said. "Obviously, they hurt, but I don't know that changing needle length will change that."

The study does raise questions, though, Gigante said. He suggested that further studies should include interviews with medical staff who do immunizations to see how often overpenetration actually occurs.

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