Thigh a better injection site for DTaP than arm

Diphtheria-tetanus-acellular pertussis (DTaP) vaccine given in the thigh to children aged 3 years and younger presents a significantly lower risk of a local reaction needing medical attention than does intramuscular (IM) injection in the arm, a new study shows.

Using data from the Vaccine Safety Datalink Project for 1.4 million children aged 1 to 6 years who received IM injections of vaccines from 2002 through 2009, researchers identified vaccinations according to method of administration (IM, subcutaneous, oral, or intranasal) and whether given alone or concomitantly with 1 other vaccine at the same site on the same day.

Analysis showed that there was little risk of reaction from single vaccines (inactivated influenza or hepatitis A) regardless of injection site. However, the risk for local reaction after DTaP vaccine, given alone or with another vaccine, was 88% higher for children aged 12 to 35 months when the shots were given in the deltoid arm muscle compared with the anterolateral thigh muscle and 41% higher for children aged 3 to 6 years. The risk of reaction did not vary by sex.

For children who received 2 IM vaccinations on the same day, with both injections in either arm or thigh, data showed a generally higher rate of injection-site reaction when DTaP was 1 of the vaccines given. However, when the vaccine combination given in the arm did not include DTaP, there was no evidence of increased risk of reaction that needed medical attention.

Overall, only 1% of children develop a reaction at the site of a shot, most often redness, pain, or swelling.

Researchers say that although they did not validate the reactions to vaccinations by medical record review and some adverse events may have been misclassified, their study suggests that vaccinations with DTaP be administered in the thigh for all children aged 12 months to 6 years.