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Get A Leg Up On DTaP Vaccine


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by Heidi Hauser Green
February 26, 2013

Let’s get real: shots hurt. Childhood vaccinations can be hard on children and parents alike. It’s natural to want to minimize the painful experience by just “getting it over with.” A shot in the arm may seem like the best way to do that—raise a sleeve, wait for the jab, slap a Band-Aid on, and you’re done. In contrast, getting a shot in the thigh, which typically involves taking the pants off of a wiggly child who’s feeling unhappy and likely kicking and flailing, may feel like a burden. But a new study suggests that there’s a good reason to make the extra effort to have your child’s vaccinations administered in the thigh—at least when it comes to the DTaP vaccine.

Led by Dr. Lisa A. Jackson, a research team looked at data collected on 1.4 million children who received a total of 6.0 million intramuscular vaccines during the study period. The researchers were able to identify which vaccinations the children received, whether they were administered in the thigh or arm, and whether they experienced a medially attended local reaction—that is, a reaction severe enough for them to seek medical follow-up within four days of vaccination. The researchers focused primarily on those vaccines that are commonly administered alone: inactivated influenza, hepatitis A, and dipthetia-tetanus-acellular pertussis (DTaP), commonly referred to as the “whooping cough” vaccine.

They found that children 12 to 35 months of age who received the DTaP injection in the thigh had a significantly lower risk of local reactions compared with those who got the shot in their arm. This raises some potential questions about common vaccination practices during routine health care visits.

Dr. Jackson and her colleagues conducted a retrospective cohort study of vaccinations received by 1.4 million children ages 1 through 5 years for whom data was available in the Vaccine Safety Datalink (VSD) between 2002 and 2009. The VSD system collects data from 10 managed care organizations across the nation, including details about vaccinations (which kind of vaccines were given and when), follow-up medical care, and patient demographics.

The team’s primary analysis looked only at vaccines administered intramuscularly by themselves, without other vaccines. A second analysis considered cases in which two vaccines were administered at the same time in the same location (thigh or arm). Children who received two vaccinations on a day with one in the thigh and one in the arm were excluded from this study, since records of adverse reaction could not link a reaction to a specific injection site.

The researchers found that adverse reactions (such as fever, crankiness, soreness at the injection site, vomiting, decreased appetite, and extended crying) were “relatively uncommon” for both the inactivated flu shot and the hepatitis A vaccination, and that there was no difference in risk due to vaccination site. For these types of vaccines, those children who received their shot in the thigh had essentially the same, low risk of adverse reaction as those who were given it in their arm.

The result for children who received the DTaP vaccination was very different. According to the research team, receiving the DTaP shot in the arm “was associated with a significantly higher risk [of adverse reaction] … compared with administration in the thigh” for children ages 1 through 5 years. When they parsed out data for younger children (those 1 and 2 years old) from older ones (ages 3, 4, and 5), they noted some differences in their findings. The increased risk of reaction with arm injection was still statistically significant for the younger group, but this was not true of the 3 to 5 year olds. A higher risk was noted for the older children, but it was not determined to be statistically significant.

A higher risk of adverse reaction for vaccination in the arm was also seen in the researchers’ analysis of children who received two vaccinations in the same limb at one time. There was, as the researchers explain, “a trend toward a higher risk of local reactions when both vaccines were given in the arm versus the thigh” when one of the vaccinations administered was the DTaP (such as when it was administered with a hepatitis A vaccine). No such increased risk was found if neither vaccination was the DTaP shot.

Current recommendations from the Advisory Committee on Immunization Practices (ACIP) of the Centers for Disease Control and Prevention (CDC) are as follows:

  • For children ages 3 to 5 years, intramuscular vaccines should be given in the arm (specifically, the deltoid muscle).
  • For children ages 12 months through 35 months of age, the preferred site of injection is the thigh (anterolateral thigh muscle). However, the deltoid can be used if the muscle mass is determined to be adequate.

This was an update of earlier recommendations that the arm muscle was the preferred site for children 1 year and older, and clinical practice has been mixed in recent years.

The current research suggests that parents and pediatricians should discuss the child’s thigh as the vaccination site when:

  • A DTaP vaccination is administered, either on its own or in combination with another vaccine AND
  • Their child is between 12 and 35 months of age.

Shots are unpleasant enough as it is. If a bit of extra effort in preparing for the shot will lead to an easier recovery afterward, and if there is no medical reason for preferring the arm over the thigh, then this change seems worthwhile.

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