Serious local reactions to fifth dose of DTaP vaccine more common in arm vs. thigh

Jackson LA. Pediatrics. 2011;doi:10.1542/peds.2010-1886.

Medically attended local reactions to the fifth dose of the diphtheria and tetanus toxoids and acellular pertussis vaccine occurred significantly more often in the arm than the thigh, though the chance of any reaction at all is rare, according to a retrospective study.

Researchers examined data of 233,161 children aged 4 to 6 years from the Vaccine Safety Datalink population. All children received a diphtheria and tetanus toxoids and acellular pertussis (DTaP) vaccination during the study period. Medically attended reactions to the vaccine were confirmed by a review of medical records, according to the study.

Overall, only 1,017 children (0.4%) had any reaction to the fifth dose of the DTaP vaccine. Children who received an injections in the arm were significantly more likely to experience a reaction requiring medical attention (47.4 per 10,000) than children who were vaccinated in the thigh (32.1 per 10,000 children) (P<.001), according to the study. Overall, arm injections conveyed a 78% higher risk of a serious local reaction.

"Our findings ... suggest that the thigh should be considered an acceptable site of injection for this vaccination," the researchers wrote.

The researchers also found a positive correlation between body mass index and increased risk of a serious local reaction at either injection site.

"The factors that contributed to this association are not clear, but a possible explanation is that adequate intramuscular injection is achieved less frequently in larger children," the researchers wrote.

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