Monday, February 15, 2010

Longer Needle May Be Preferred for HBV Vaccination of Obese Teens

From Medscape Medical News
Laurie Barclay, MD

February 8, 2010 — Use of a longer needle results in significantly higher titers in response to hepatitis B virus (HBV) vaccine among obese adolescents, according to the results of a randomized study reported online in the February 8 issue of Pediatrics.

"Obese youth achieve lower titers than average-weight peers in response to hepatitis B vaccine when a 1-inch needle is used," write Amy B. Middleman, MD, MSEd, MPH, from Baylor College of Medicine in Houston, Texas, and colleagues.

The goal of the study was to evaluate whether using a longer (1.5-inch) vs a standard (1-inch) needle to penetrate the thicker deltoid fat pad among obese youth who had not previously received the HBV vaccine would achieve higher antibody titers after immunization against HBV. The investigators randomly assigned 65 obese adolescents from a large metropolitan area to be immunized with HBV vaccine using either a 1-inch or a 1.5-inch needle. Analyzable data were available for 10 adolescents in the 1-inch needle group and for 14 in the 1.5-inch needle group.

Compared with obese adolescents immunized with a 1-inch needle, those who were immunized with a 1.5-inch needle had significantly higher antibody titers to hepatitis B surface antigen (median titers 189.8 mIU/mL with the 1-inch needle; 345.4 mIU/mL with the 1.5-inch needle; P = .03).

"This finding supports the hypothesis that needle length accounts for a significant portion of the discrepancy in immune response to HBV vaccine that is seen among those with obesity," the study authors write.

Limitations of this study include sample size smaller than planned with loss of participants to follow-up, few male participants, limited ability to enroll patients who had not yet received HBV vaccine, and limited variability in race and ethnicity (most participants were Hispanic).

"As we continue to experience high rates of obesity in the United States and throughout the world, additional evidence-based research on optimizing the effective delivery of immunizations to adolescents and young adults will be critical," the study authors conclude. "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."

This project was funded by the SAM/APA/CDC Adolescent Special Immunization Projects Award, 2001, and, in part, by the Maternal and Child Health Bureau (Title V, Social Security Act), Health Resources and Services Administration, Department of Health and Human Services. GlaxoSmithKline donated all vaccine doses. The study authors have disclosed no relevant financial relationships.

Pediatrics. Published online February 8, 2010.

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