Background: Vaccine injections are the most common reason for iatrogenic pain in childhood. With the steadily increasing number of recommended vaccinations, there has been a concomitant increase in concern regarding the adequacy of pain management. Physical interventions and injection techniques that minimize pain during vaccine injection offer an advantage over other techniques because they can be easily incorporated into clinical practice without added cost or time. Their effectiveness, however, has not previously been studied using a systematic approach.
Objective: The purpose of this review was to determine the effectiveness of physical interventions and injection techniques for reducing pain during vaccine injection in children.
Methods: MEDLINE, EMBASE, CINAHL, and the Cochrane Central Register of Controlled Trials databases were searched to identify randomized controlled trials (RCTs) and quasi-RCTs that determined the effect of physical interventions and injection techniques on pain during injection of vaccines in children 0 to 18 years of age, using validated child self-reported pain or assessments of child distress or pain made by others (parent, nurse, physician, observer). We sought to determine the effects of: (1) different formulations of the same vaccine; (2) position of the child during injection; (3) intramuscular versus subcutaneous injection; (4) cooling of the skin at the injection site with ice before injection; (5) stroking the skin or applying pressure close to the injection site before and during injection; (6) order of vaccine injection when 2 vaccines were administered sequentially; (7) simultaneous versus sequential injection of 2 vaccines; (8) vaccine temperature; (9) aspiration before injection; (10) anatomic location of injection; (11) aspects of the needle (gauge, length, angle of insertion, speed of injection); and (12) combinations of these interventions. All meta-analyses were performed using a fixed-effects model.
Results: Nineteen RCTs involving 2814 infants and children (0–18 years of age) were included in the systematic review. One study included children ≥16 years and adults (n = 150). Interventions with positive findings are summarized here. In 2 trials that used child self-reports of pain during administration of measles-mumps-rubella vaccine (total, 680 children with complete data), the Priorix vaccine caused less pain than the M-M-RII vaccine (standardized mean difference [SMD], −0.66; 95% CI, −0.81 to −0.50; P < 0.001). In 3 trials (404 children), the number needed to treat (NNT) with Priorix to prevent 1 child from crying was 3.2 (95% CI, 2.6–4.2). In 4 trials (281 infants and children), sitting children up or having parents hold infants appeared to cause less pain than the supine position, but the difference was not statistically significant; however, significant heterogeneity was found among the studies, and a qualitative approach was used for data analysis. A benefit was observed for 3 of the 4 studies; the SMD ranged from −0.4 to −0.8 (P < 0.05 for all analyses). The negative findings observed for the remaining study may have been the result of methodologic heterogeneity. Stroking the skin close to the injection site before and during injection reduced pain in 1 trial (66 children; SMD, −0.53; P = 0.03). One study (120 children) found that when diphtheria-polio-tetanus-acellular pertussis-Haemophilus influenzae type b (DPTaP-Hib; Pentacel) and pneumococcus (Prevnar) were injected sequentially during the same office visit, observer- and parent-reported pain scores were lower when DPTaP-Hib was injected first (SMD, −0.40 and −0.57, respectively; P ≤ 0.03). In 1 study (113 infants) comparing rapid intramuscular injection without aspiration and slow intramuscular injection with aspiration, the rapid injection without aspiration was associated with less pain (SMD, −0.62 to −0.97 for parent, nurse, physician, and observer behavioral pain ratings; all, P < 0.05). The NNT to prevent 1 infant from crying was 2.5 (95% CI, 1.8–4.3).
Conclusions: Pain during immunization can be decreased by: (1) injecting the least painful formulation of a vaccine; (2) having the child sit up (or holding an infant); (3) stroking the skin or applying pressure close to the injection site before and during injection; (4) injecting the least painful vaccine first when 2 vaccines are being administered sequentially during a single office visit; and (5) performing a rapid intramuscular injection without aspiration.
