For 14 of the 18 questions, there was sufficient evidence to make a practice recommendation to reduce pain (). These recommendations have been organized into five clusters: infants, injection procedure, parent-led strategies, pharmacotherapy and psychological strategies. For the remaining four clinical questions, there was insufficient evidence to make a practice recommendation ().
Recommendations to reduce pain during vaccine injections in children*
Interventions without sufficient evidence to make a recommendation regarding their use to reduce pain during vaccine injections in children
Several of the practice recommendations relating to the injection procedure can be implemented immediately by health care providers in all vaccination practice settings, as they do not require planning or additional resources (e.g, time, supplies or money). Examples of these easily adopted pain-relieving strategies include performing intramuscular injections rapidly without prior aspiration, positioning children upright, injecting the most painful vaccine last when multiple vaccines are being administered and providing tactile stimulation.
Performing intramuscular injections rapidly without prior aspiration probably reduces pain through the combined effects of shortening the time of contact between needle and tissue and reducing lateral movement of the needle (“wiggle”) within the tissue. The long-standing practice of aspiration was initially proposed to reduce the risk of intravascular injection of the vaccine. However, the sites commonly used for vaccine injections are devoid of large blood vessels, and aspiration is no longer regarded as necessary. About one-third of vaccinators do not perform aspiration, and there have been no documented harms caused by omitting this step.
Positioning children upright or holding them during vaccine injections, rather than laying them supine, reduces pain. Children can be seated or held by a parent in a position that is most comfortable for them (e.g., held in a bear hug or on the parent’s lap). Although the exact mechanism underlying the reduction in pain associated with this positioning is unknown, it may involve a reduction in anxiety, which in turn reduces the perception of pain. Conversely, excessive restraint may increase the child’s distress, so parents and health care providers are encouraged to hold and support children without using excessive force.
Children routinely receive two or more vaccine injections during the same visit. Administering the most painful vaccine last minimizes the priming effect of the first injection on subsequent injections, thus reducing overall pain. There is limited research, however, regarding the optimal order of injection for vaccines that are coupled for administration at the same visit. At present, the two vaccines known to be relatively more painful are M-M-R-II (Merck) and Prevnar (Wyeth). When these are coupled with other vaccines, they should be given last.
Providing tactile stimulation by rubbing or stroking the skin near the injection site before and during vaccine injections reduces pain in children aged four years and older. The proposed mechanism involves blocking the transmission of the pain sensation to the brain by means of competing touch sensation. This technique is often referred to as generating “white noise.” The optimal method for rubbing (in terms of frequency, intensity and pattern) is unknown. It should be tailored to the request and comfort level of the individual child.
A few practice recommendations in this guideline, such as breastfeeding or administration of sugar water (for infants) and application of topical anesthetics and psychological interventions (for children of all ages), require some planning or additional resources, or both, on the part of health care providers and children and their families. Health care providers are encouraged to discuss these additional options with parents and children (as appropriate) and to select the strategies best suited to individual children.
Breastfeeding is considered a combined analgesic intervention because several aspects of breastfeeding (e.g., holding the child, skin-to-skin contact, the sweet-tasting milk and the act of sucking) attenuate pain responses. An adequate latch must be established before the injection. This may take about one minute. If an adequate latch cannot be established before the injection or the infant is not being breastfed, sugar water can be administered instead. The mechanism of action of sugar water, although not fully elucidated, may involve release of endogenous opioids through activation of sweet taste receptors and distraction. Sugar water is easily prepared by mixing a packet of sugar with 10 mL (two teaspoons) of water and feeding some to the infant a minute or two before the injection. The infant should be monitored for minor adverse events such as choking or gagging.
Topical anesthetics block the transmission of pain signals from peripheral nociceptors. They are effective for vaccines that are administered intramuscularly and subcutaneously. At present, limited evidence indicates that these agents do not interfere with the immunogenicity of the vaccine. Topical anesthetics are available for purchase without a prescription, and parents have indicated a willingness to pay for them to mitigate the pain associated with vaccine injection in their children. However, parents require education about the use of these agents, including the exact site or sites of administration, the duration of application and possible adverse effects. Topical anesthetics must be applied ahead of time, about 20–60 minutes before the injection, depending on the commercial product being applied. The topical anesthetic can be applied upon arrival at the clinic or school (by a parent or a qualified health care professional or delegate) or before departure from home. If multiple vaccines are being injected during the same visit, the topical anesthetic can be applied at two separate sites (e.g., right and left legs). The vaccine or vaccines must be injected where the anesthetic has been applied. Health care providers can use a nontoxic marker to outline the area of application. The cost per dose is $5–$10. Transient changes in skin colour are common. Systemic toxicity is rare but can occur if the dose or the duration of application is excessive.
Distraction is a psychological intervention that involves directing the child’s attention away from the procedure. Distraction led by a health care provider is effective for children of all ages. For children three years of age and older, self-led distraction is also effective. Distraction led by a parent is less effective, possibly because the parent has difficulty providing distraction when he or she is also distressed. The panel recommends, however, that clinicians discuss parent-led interventions, including distraction and coaching, on the grounds that some benefits have been observed in terms of general pain-related distress. In addition, parents may benefit from a formal role, and there may be limited availability of other individuals to deliver such interventions. It is important to ensure that age-appropriate distraction strategies are used and that children are engaged with them. When appropriate, involve the child in planning which distraction strategy will be used and in directing the distraction strategy. Examples of distraction strategies include toys (for infants), bubbles (for toddlers), video games (for school-age children) and music (for adolescents).
Deep (tummy) breathing is another effective psychological intervention that can be used for children three years of age and older. Deep breathing can be facilitated by having the child blow bubbles or spin pinwheels with the breath. These aids also act as distraction strategies.
Pain relief is enhanced when individual pain-relieving strategies are combined. Therefore, health care providers are encouraged to use a mix of strategies to mitigate pain. Parents can be enlisted to help combine and coordinate many of these strategies. In particular, parents can prepare their children, apply topical anesthetics, bring a distraction aid to the appointment, coach the child during deep breathing and hold the child.
Additional details of the practice recommendations, including evidence summaries, references and clinical considerations, can be found in the full guideline (www.cmaj.ca/cgi/doi/10.1503/cmaj.101720