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OBJECTIVE: To assess whether the risk of medically attended local reactions to the fifth dose of the diphtheria and tetanus toxoids and acellular pertussis (DTaP) vaccine varies according to injection site (arm versus thigh). METHODS: We conducted a retrospective cohort study of children aged 4 through 6 years in the Vaccine Safety Datalink population who received a DTaP vaccination during the period from 2002 through 2006. Medically attended local reactions to the DTaP vaccine were presumptively identified from administrative data and were confirmed by medical record review. RESULTS: Among the 233 616 children in the study population, 1017 (0.4%) had a confirmed medically attended local reaction to the fifth dose of the DTaP vaccine. The rate of those reactions was significantly higher with vaccinations given in the arm (47.4 per 10 000 vaccinations) compared with vaccinations given in the thigh (32.1 per 10 000 vaccinations) (P < .001). In a multivariable analysis adjusted for age, gender, and study site, children vaccinated in the arm had a 78% higher risk of a local reaction (relative risk: 1.78 [95% confidence interval: 1.43–2.21]). CONCLUSIONS: Local reactions to the fifth dose of the DTaP vaccine that require medical evaluation are uncommon, but the risk of those reactions is significantly higher when the vaccine is injected in the arm. These findings suggest that the thigh should be considered as an acceptable site of injection for this vaccination.

OBJECTIVE. Local reactions are relatively common after the fifth diphtheria-tetanus-acellular pertussis vaccination, but factors associated with an increased risk of those reactions are not well defined. The objective of this study was to assess the relationship between needle length and injection site on the risk of local reactions to the fifth diphtheria-tetanus-acellular pertussis vaccination administered in the context of usual clinical care.METHODS. In this prospective assessment, parents reported signs and symptoms of adverse events for 7 days after vaccination. The relative risk of adverse events in relation to needle length (16 or 25 mm) and injection site (arm or thigh) was estimated in multivariate analyses that adjusted for age, gender, and BMI.RESULTS. Of the 1315 study participants, 89% were vaccinated in the arm, and 67% were vaccinated with a 25-mm needle. Among children vaccinated in the arm, use of the shorter 16-mm needle was associated with a significantly higher risk of any redness, ≥5 cm of redness, persistent redness on day 2, and pain compared with vaccination with a 25-mm needle. Similar trends among the smaller group of children vaccinated in the thigh were also suggested but were not statistically significant. In analyses that were restricted to children vaccinated with a 25-mm needle, vaccination in the thigh versus arm was associated with a substantially lower risk of ≥5 cm of redness and a significantly lower risk of swelling and any itching but not with any difference in the risk of pain, irritability, or change in activity.CONCLUSIONS. These findings suggest that a 25-mm needle should be used for the fifth diphtheria-tetanus-acellular pertussis vaccination regardless of injection site and that vaccination in the thigh is an option that may be considered by parents and providers who would like to decrease the risk of local reactions characterized by redness and swelling.

BACKGROUND. The frequency of local vaccination reactions increases with successive doses of diphtheria-tetanus toxoids-acellular pertussis (DTaP) vaccine, and local reactions occur for the majority of children receiving the fifth DTaP vaccination. It is not known whether these reactions can be prevented with prophylactic use of acetaminophen or ibuprofen. METHODS. In this 3-group, randomized, blinded, controlled trial, 372 children were assigned randomly, in a 2:2:1 ratio, to receive 3 doses of acetaminophen, ibuprofen, or placebo. The first dose of study medication was administered within 2 hours before the fifth DTaP vaccination, and the remaining 2 doses were given at 6-hour intervals. The primary outcome measures included a local reaction with an area of redness or discoloration ≥5 cm in diameter on the evening of or during the 2 days after vaccination, an increase in mid-limb circumference of ≥2 cm on the evening of or during the 2 days after vaccination, and a persistent local reaction, defined as an area of redness or discoloration present on the third day after vaccination. RESULTS. Local reactions with a ≥5-cm area of redness or discoloration were reported for 35% of children in the placebo group, compared with 33% of children in the acetaminophen group and 37% of children in the ibuprofen group. There was also no significant difference between the placebo and treatment groups in the proportions of children with a ≥2-cm increase in mid-limb circumference or with a persistent local reaction. CONCLUSIONS. We did not find evidence that prophylaxis with acetaminophen or ibuprofen offers a clinically significant benefit in prevention of local reactions to the fifth DTaP vaccination.