Longer needle length may boost efficacy of vaccine in obese adolescents

Longer, 1.5-inch needles yielded better results in obese adolescents after immunization with hepatitis B vaccine, when compared with standard needles, according to the results of a study published online.

“Multiple hypotheses have been offered for disparity in vaccine immune response on the basis of BMI, including the possibility that standard needle length recommendations do not account for the increased length needed to penetrate the deltoid fat pad and into the muscle of obese adolescents and adults,” researchers wrote in the study.

From December 2001 to October 2004, researchers enrolled 24 patients, aged 14 to 24 years, at city clinics, a health fair and a high school in Houston. The researchers randomly assigned one group of 14 patients to the 1.5-inch needle group and the remaining 10 patients to the 1-inch needle group.

The researchers noted that the 1.5-inch needles produced significantly higher hepatitis B surface antigen (median, 345.3 mIU/mL) in the patients when compared with the group that received the 1-inch needles (median, 189.8 mIU/mL).

“This supports the hypothesis that inadequate muscle penetration is responsible, at least in part, for lower immune response to [hepatitis B] vaccine among obese adolescent and adult vaccine recipients,” the researchers wrote. “Following updated needle length recommendations will be a first step toward improving the health of our youth and young adults by preventing vaccine-preventable diseases.”

Middleman AB. Pediatrics. 2010;125:e000.