Quality of Included Studies and Risk of Bias
The methodologic quality (Risk of Bias) assessments for the critical outcomes of the included studies are presented in Table 3. Depending on the intervention evaluated, the overall Risk of Bias varied from high (eg, for breastfeeding and vapocoolants because of lack of blinding) to unclear (eg, for topical anesthetics and sweet-tasting solutions as there was insufficient information to make judgments) to low Risk of Bias (for acetaminophen based on a single study).
Overall Quality of Evidence and Treatment Effects
A quantitative summary of the treatment effects for available critical outcomes are described below. For several clinical questions, multiple indicators of the same critical outcome were included (eg, distress measured in the preprocedure phase of the procedure, the acute phase, or the recovery phase, or various combinations of these). For the purposes of presentation, the critical outcome indicators with the most number of participants are included. If the critical outcome was distress, the acute and the acute and recovery phases were also prioritized over other indicators of distress for presentation. Further, a qualitative summary across all critical outcomes is presented in Table 4. Information on immunogenicity (important outcome) is summarized in Table 5 while information on other important outcomes (adverse events, fidelity, feasibility, and preference) is presented in Table 6. Supporting GRADE Evidence Profiles and Summary of Findings tables (Tables, Supplemental Digital Content 1 to 14) and accompanying Forest plots (Figures, Supplemental Digital Content 1 to 14) for critically important and important outcomes are included as Supplemental Digital Content.
Should Breastfeeding be Used During Vaccine Injections in Children 0 to 2 Years?
The analgesic effect of breastfeeding was examined in 9 trials22–27,29,30,33 including data on 858 infants (0 to 12 mo). In all studies, breastfeeding was commenced immediately before vaccination and continued during and afterward. In the included trials, the comparator arm varied from the infant being swaddled in the bassinet/placed on the table24,26 held in the mother’s arms,27,29 restrained by the mother,22 given distilled water25 to a no intervention roup.23,30,33
Benefit of breastfeeding was observed for all the critical outcomes analyzed, including acute and acute plus recovery distress (Table and Figure, Supplemental Digital Content 1, http://links.lww.com/CJP/A249). The SMD was −1.78 (CI, −2.35, −1.22) for acute distress (n=792; data from 8 studies).22,23,25–27,29,30,33 For distress during the acute plus recovery phase (n=424) the SMD was −1.89 (CI, −3.19, −0.59). Considerable heterogeneity was reported for this outcome, which can be explained by the potential differences in the implementation of the intervention (breastfeeding and the control group) and age of the infant (studies included infants less than 24 h of age to up to 12 mo). There was low to very low quality of evidence due to methodologic limitations of the included studies (Table, Supplemental Digital Content 2, http://links.lww.com/CJP/A250).
If Breastfeeding is Not Used During Vaccine Injections, Should Breastfeeding be Used Before Vaccine Injections in Children 0 to 2 Years?
Two trials34,35 including 100 infants (6 wk to less than 3 mo of age) evaluated the effect of breastfeeding before vaccination. Breastfeeding ceased 2 to 60 minutes before injection.34,35 The control group included holding34 or no intervention.35 The results were mixed (Table and Figure, Supplemental Digital Content 3, http://links.lww.com/CJP/A251). Breastfeeding prevaccine injection was associated with lower acute distress: SMD −1.43 (CI, −2.14, −0.72) as well as acute plus recovery distress combined: SMD −1.47 (CI, −2.05, −0.90) (Figure, Supplemental Digital Content 4, http://links.lww.com/CJP/A252). No benefit was noted for distress recovery. The quality of evidence ranged from moderate to low quality (Table, Supplemental Digital Content 5, http://links.lww.com/CJP/A253).
Should Topical Anesthetics be Applied Before Vaccine Injections in Children 0 to 12 Years?
Fifteen studies23,34,36–46,48,49 including infants and children investigated the effect of topical anesthetics. In 10 included studies, vaccines were administered intramuscularly34,37–39,41,42,44,45,48,49; in 2 studies,43,46 they were administered subcutaneously; and in 3 studies,23,36,40 both intramuscular (IM) and SC vaccines were given. Lidocaine-prilocaine cream 5% was applied in 11 studies,23,34,36,37,39–42,44,47,48 lidocaine-prilocaine patch 5% was applied in 3 studies,38,43,44 whereas amethocaine gel 4% was applied in 1 study.46 The majority of studies (n=8) included a placebo.36,38,41–43,45,47,48 A meta-analysis of 13 studies23,34,36–39,42–46,48,49 including 1424 infants demonstrated lower levels of acute distress in the topical anesthetics group: SMD −0.91 (CI, −1.36, −0.47). Observer-rated acute distress for child was lower in the topical anesthetics group: SMD −1.13 (CI, −1.78, −0.47) in 1 study including 42 children.41 For distress during the acute plus recovery phase (n=546) the SMD was −0.68 (CI, −1.24, −0.13). The results were mixed for other indicators of distress. A meta-analysis of 3 studies38,39,41 including 269 children between 4 and 11 years showed no benefit of topical anesthetics on self-report of pain: SMD −0.29 (CI, −0.64, 0.05). However, removal of the data from 1 study with a high Risk of Bias39 altered the result in favor of topical anesthetics: SMD −0.47 (CI, −0.73, −0.21). The SMD (CI) for fear was 0.04 (CI, −0.29, 0.37; n=68) (Table and Figure, Supplemental Digital Content 6, http://links.lww.com/CJP/A254). The quality of evidence ranged from moderate to very low (Table, Supplemental Digital Content 7, http://links.lww.com/CJP/A255).
Should Topical Anesthetics be Applied Before Vaccine Injections in Adolescents Older than 12 Years and Adults?
Two studies50,51 evaluated the analgesic effects of topical anesthetics in adolescents older than 12 years and adults. Pain was lower in the topical anesthetic group: SMD −0.85 (CI, −1.38, −0.32) in the study by Taddio et al,51 whereas acute distress was not lower: SMD 0.05 (CI, −0.31, 0.41) in the study by Hansen et al50 (Table and Figure, Supplemental Digital Content 8, http://links.lww.com/CJP/A256). The quality of evidence was moderate (Table, Supplemental Digital Content 9, http://links.lww.com/CJP/A257).
Three trials,43,44,46 including 445 infants and children assessed antibody response following vaccination. Results are presented in Table 5. There was no difference in the immune response to vaccine in topical anesthetics compared with placebo group for Measles-Mumps-Rubella, diphtheria-tetanus-acellular pertussis-inactivated poliovirus-Haemophilus influenzae type b, and hepatitis B. In a separate study, Dohlwitz et al83 reported no effect of topical anesthetics on Bacillus-Calmette-Guérin vaccine response in 388 children.
Should Topical Anesthetics be Used Before Vaccine Injections in Combination With Breastfeeding During Vaccine Injections (Rather than Topical Anesthetics or Breastfeeding Alone) in Children 0 to 2 Years?
In one study42 including 60 infants less than 3 months of age, topical anesthetics combined with breastfeeding were compared with topical anesthetics alone during vaccine injections. Distress was the critical outcome. The results were mixed (Table and Figure, Supplemental Digital Content 10, http://links.lww.com/CJP/A258). The combination of topical anesthetics preinjection and breastfeeding during injection did not reduce distress in the acute phase of the procedure (SMD: −0.35 [CI, −0.86, 0.16]); however, distress during the acute plus recovery phase of the procedure was reduced (SMD: −0.83 [CI, −1.36, −0.30]) (Figure, Supplemental Digital Content 11, http://links.lww.com/CJP/A259). The quality of evidence was low (Table, Supplemental Digital Content 12, http://links.lww.com/CJP/A260).
Should Sucrose Solution be Given Before Vaccine Injections in Children 0 to 2 Years?
Eighteen studies including infants and young children aged 2 weeks to 48 months investigated the effects of sucrose.23,35,52–58,60–62,64–69 The concentration of sucrose ranged from 12% to 75% except for the study by Chattopadhyay et al54 where the concentration of sucrose was described as a “saturated solution.” The majority of studies (n=9) used sucrose in the concentration of 20% to 33%.35,55–58,61,62,67,69 Except for 3 studies,52,57,58 all used a volume of 2 mL. The majority of studies (n=15) administered sucrose 2 minutes before the procedure.23,35,52,53,55–58,61,62,64–67,69
In a meta-analysis including 881 infants, sucrose was associated with lower acute distress: SMD −0.37 (CI, −0.67, −0.06). Similarly, acute plus recovery distress score was lower in the sucrose group: SMD −0.76 (CI, −1.19, −0.34); n=2071 (Table and Figure, Supplemental Digital Content 13, http://links.lww.com/CJP/A261). The RR (CI) for dichotomous outcome of acute distress was 0.37 (CI, 0.2-0.69) (Figure, Supplemental Digital Content 14, http://links.lww.com/CJP/A262). The quality of evidence of included studies was high to moderate (Table, Supplemental Digital Content 15, http://links.lww.com/CJP/A263).
Benefit of sucrose in the concentration of 50% or 70% was observed for all the critical outcomes analyzed, including acute distress and acute plus recovery distress. The SMD (CI) were −0.31 (−0.61, −0.02; n=259 infants) for acute distress; and −1.43 (−2.34, −0.52; n=1006 infants) for acute plus recovery distress. Mixed results were found for sucrose in the concentration of 20% to 33%. Benefit was observed for the acute plus recovery (SMD −0.85 [CI, −1.6, −0.11]) and recovery phases (SMD −1.13 [CI: −1.89, −0.37]). There was no evidence of a benefit of sucrose in the concentration of 12% across all indicators of distress analyzed (Table and Figure, Supplemental Digital Content 13, http://links.lww.com/CJP/A261).
Should Glucose Solution be Given Before Vaccine Injections in Children 0 to 2 Years?
Six trials25,70–74 investigated the effect of glucose on vaccine injection pain in infants 12 hours to 12 months. The concentration of glucose was 25% in 3 studies,25,70,72 30% in 2 studies,73,74 and 50% in 1 study.71 The volume administered ranged from 1 to 2 mL and timing varied from 2 minutes before to immediately prior the procedure. The results were mixed (Table and Figure, Supplemental Digital Content 16, http://links.lww.com/CJP/A264). In a meta-analysis including all trials (n=818 infants), acute plus recovery distress was lower in the glucose group: SMD −0.69 (CI, −1.03, −0.35). There was no evidence of a benefit of glucose on acute distress (n=520): SMD −0.59 (CI, −1.38, 0.20) (Table and Figure, Supplemental Digital Content 16, http://links.lww.com/CJP/A264). The quality of evidence ranged from high to moderate (Table, Supplemental Digital Content 17, http://links.lww.com/CJP/A265).
Should Sweet-tasting Solutions (Sucrose, Glucose) be Used Before Vaccine Injections in Combination With Non-Nutritive Sucking (Finger/Thumb, Pacifier) During Vaccine Injections (Rather than Sweet-tasting Solutions or Non-Nutritive Sucking Alone) in Children 0 to 2 Years?
One study73 including 74 infants 3 months of age compared the effect of sweet-tasting solutions (glucose) before vaccine injection and non-nutritive sucking during vaccine injection to sweet-tasting solution or non-nutritive sucking alone. There was no evidence of benefit of the combination of glucose and non-nutritive sucking (pacifier) compared with glucose or non-nutritive sucking (pacifier) alone across all indicators of distress evaluated. For acute plus recovery, the SMD was −0.32 (CI, −0.79, 0.15) and the RR was 0.99 (CI, 0.78, 1.26) (Table and Figure, Supplemental Digital Content 18, http://links.lww.com/CJP/A266). The included study did not assess treatment fidelity with non-nutritive sucking. The quality of evidence was very low (Table, Supplemental Digital Content 19, http://links.lww.com/CJP/A267).
Should Breastfeeding and Sweet-tasting Solutions (Sucrose, Glucose) be Combined Together Before Vaccine Injections (Rather than Breastfeeding or Sweet-tasting Solutions Alone) in Children 0 to 2 Years?
One study35 including 90 infants aged less than 3 months evaluated the effect of a combination of breastfeeding and sweet-tasting solutions (sucrose) versus breastfeeding or sucrose alone. There was no evidence of a benefit of breastfeeding and sucrose versus either alone across all indicators of distress, The SMD for acute distress was 0.28 (CI, −0.34, 0.90) and for acute recovery it was 0.06 (CI, −0.37, 0.5) (Table and Figure, Supplemental Digital Content 20, http://links.lww.com/CJP/A268). The quality of evidence was low (Table, Supplemental Digital Content 21, http://links.lww.com/CJP/A269).
Should Vapocoolants be Applied Before Vaccine Injections in Children 0 to 3 Years?
One study75 including 60 infants between 6 weeks and 3 months investigated the effect of vapocoolant versus control (compressed air spray). In this study, the vapocoolant and placebo were both sprayed on the injection site for 2 to 3 seconds right before injection. Vapocoolant spray did not reduce acute distress (the only indicator of distress included in the study): SMD −0.44 (CI, −0.96, 0.07) (Table and Figure, Supplemental Digital Content 22, http://links.lww.com/CJP/A270). The quality of evidence was low (Table, Supplemental Digital Content 23, http://links.lww.com/CJP/A271).
Should Vapocoolants be Applied Before Vaccine Injections in Children Older than 3 to 17 Years?
Five trials were included in the systematic review.41,76–79 In 3 trials,41,76,77 the vapocoolant was applied to the injection site using sterile cotton ball for 10 to 20 seconds, whereas in the other 2 trials, the vapocoolant was sprayed directly on the site with application time of 3 to 7 seconds.78,79 The control group consisted of placebo spray, distraction, or a no intervention group. In a meta-analysis of 4 trials including 228 children, there was no evidence of a benefit on pain: SMD −0.38 (CI, −0.89, 0.13) (Table and Figure, Supplemental Digital Content 24, http://links.lww.com/CJP/A272). The quality of evidence was low (Table, Supplemental Digital Content 25, http://links.lww.com/CJP/A273).
Should Vapocoolants be Applied Before Vaccine Injections in Adults?
One trial80 including 185 adults was identified for inclusion in the review. A cotton ball saturated with vapocoolant or cold saline (4°C) was applied for 15 seconds in the arm. Acute pain was lower in the vapocoolant group: SMD −0.78 (CI, −1.08, −0.48) (Table and Figure, Supplemental Digital Content 26, http://links.lww.com/CJP/A274). The quality of evidence was low (Table, Supplemental Digital Content 27, http://links.lww.com/CJP/A275).
Should (Oral) Acetaminophen be Given Before Vaccine Injections in Individuals of all Ages?
No trial evaluating the effectiveness of orally administered acetaminophen for vaccine injection pain was identified, and indirect evidence was obtained from the closest related needle procedure (SC injection into an implanted intravenous port).81 The study population included 51 infants and children (1 to 18 y of age) with cancer randomized to acetaminophen or placebo 60 minutes before the procedure. All children in both the groups also received lidocaine-prilocaine patch/cream. There was no difference in pain between groups: SMD −0.64 (CI, −1.43, 0.15) (Table and Figure, Supplemental Digital Content 28, http://links.lww.com/CJP/A276). The quality of evidence was low (Table, Supplemental Digital Content 29, http://links.lww.com/CJP/A277).
Five studies84–88 evaluated the effect of prophylactic acetaminophen/paracetamol (administered at the time or just after the vaccine) on immune response to vaccination. Results from these studies are presented in Table 5. In 3 trials including 442 adults, the use of prophylactic acetaminophen did not affect the immune response to influenza vaccine as measured using the hemagglutination inhibition antibody assay.84,85,87
In the study by Doedée et al,86 use of prophylactic paracetamol was associated with a 26% reduction in antihepatitis B surface antigen antibody levels in 178 adults even though all participants achieved levels of >10.0 IU/L (considered to be seroprotective). Prophylactic paracetamol was associated with reduction in immune response to DTPa+HBV+IPV/Hib (hexavalent diphtheria-tetanus-3 component acellular pertussis-hepatitis B-inactivated poliovirus type 1, 2, and 3-Haemophilus influenzae type b); and PHiD-CV (10-valent pneumococcal nontypeable Haemophilus influenzae protein D-conjugate vaccine) in 459 children.88
Should (Oral) Ibuprofen be Given Before Vaccine Injections in Individuals of all Ages?
No trial was identified that evaluated orally administered ibuprofen for vaccine injection pain, and evidence was obtained from a cross-over trial that compared the effectiveness of ibuprofen 5% cream to lidocaine-prilocaine 5% cream in 20 adults undergoing venipuncture.82 Lidocaine-prilocaine 5% cream was superior to ibuprofen cream in preventing the pain associated with venipuncture: SMD 0.77 (CI, 0.06, 1.48) (Table and Figure, Supplemental Digital Content 30, http://links.lww.com/CJP/A278). The quality of evidence was very low (Table, Supplemental Digital Content 31, http://links.lww.com/CJP/A279).
No studies have evaluated the effect of oral ibuprofen on immune response to vaccines.
In this systematic review and meta-analysis, we examined the effectiveness of various pharmacological interventions and combined interventions for vaccine injection pain in individuals across the lifespan. These interventions included breastfeeding during and before vaccine injection, topical anesthetics, sweet-tasting solutions (sucrose and glucose), vapocoolants, oral analgesics (acetaminophen and ibuprofen), and the combination of 2 interventions versus 1 intervention. We found evidence for a benefit of breastfeeding, topical anesthetics, sweet-tasting solutions, and combinations of topical anesthetics and breastfeeding for reducing vaccine injection pain in infants and children. In adults, limited data demonstrate some benefit of topical anesthetics and vapocoolants.
This review found evidence of a benefit of breastfeeding. These findings are consistent with those reported in our previous review and clinical practice guideline6,8 and a Cochrane review including neonates undergoing needle procedures.89 Breastfeeding is a simple and cost-neutral intervention that can be easily adopted across vaccination settings by caregivers and health care professionals. It provides analgesia through several mechanisms including comfort (close proximity to the mother), distraction, and stimulation of the orotactile and mechnoreceptors (sucking on the breast),90 and presence of sweet-tasting substances in the mother’s milk.91–93 Exclusive breastfeeding until 6 months is recommended by the World Health Organization due to the nutritional and psychological benefits of breastfeeding; and supports breastfeeding for 2 years or beyond.94 The analgesic effects of breastfeeding further promote breastfeeding as the method of choice for infant feeding.
For the intervention to be effective, an adequate latch should be established before and continued during and after the procedure. This may not be always possible to achieve as the infant may be sleepy or not interested in feeding or not hungry and an alternative pain management strategy should be considered.
Breastfeeding Prevaccine Injection
If breastfeeding cannot be achieved during the procedure, breastfeeding prevaccine injection should be encouraged as it has some benefits on distress secondary to satiation of the infant.34,35 There are no data regarding breastfeeding before and during vaccine injections. It is possible that breastfeeding before may cause less infants to latch during the vaccine injections.
Topical anesthetics were effective in reducing pain associated with vaccine injections administered by various routes including intramuscular and subcutaneous in children and adults. This conclusion was based on 17 studies which predominantly used a comparator of placebo. In terms of mechanism, topical anesthetics temporarily inhibit the generation and transmission of pain impulses by blocking the action potentials across nerve endings located in the dermis.95 By producing dermal analgesia (topical local anesthetics penetrate to a depth of ~5 mm below the skin surface), they effectively reduce the pain from needle puncture.
Despite their proven effectiveness, topical anesthetics are not used in clinical practice as part of standard care. Topical anesthetics require an application time of 20 to 60 minutes depending on the commercial preparation that is used. This is an obstacle to clinical use. However, if there is insufficient waiting time at the clinic, they can be applied ahead of time. In 2 studies included in this review,38,48 instructions were provided to parents on how to apply the cream at home on the day of vaccination. In the study by Cassidy et al,38 54/161 (86%) of the parents applied the topical anesthetic correctly and in the study by Taddio et al,48 96/100 (96%) of the parents applied it correctly. Further, 84/96 (88%) parents reported that they could fit the application of the cream in their schedules and 87 (91%) reported that the cream was not difficult to apply.48 Our findings regarding the feasibility of home application is consistent with other studies in which topical anesthetics have been applied at home by parents before venipuncture required for minor day care surgeries (eg, endoscopy) provided optimal education was given.96,97 Two studies reported on the mean waiting time before vaccine injection in the clinics demonstrating feasibility of application of topical anesthetics onsite. In the study by Abuelkheir et al36 (Saudi Arabia), the mean waiting time before the vaccine injection was 57 minutes (SD=16.7), whereas in the study by Taddio et al98 (Canada), the mean waiting time reported was 41.6 minutes (SD=28.6). Application of the topical anesthetics while awaiting the appointment is possible if there is sufficient time. This also allows clinicians to assist in their administration (eg, ensuring they are placed in the correct anatomic location).
The cost of topical anesthetics requires some discussion. The cost of EMLA patch is ∼Canadian $12, while the cost of a 60 g tube is ∼$50 which can be used for multiple applications. At present, individuals are usually asked to absorb their cost. It is generally assumed that individuals would not pay, however, there are some data suggesting they would. In 1 included study, parents were willing to pay $11.90 for topical anesthetics for future injections.41 In another study by Ughasoro et al99 caregivers were willing to pay $8.31 for topical anesthetics which is more that the cost of the cream itself.
Several practical issues should be addressed before its adoption in clinical practice including: (1) ease of availability over the counter depending on geographic location (eg, in USA topical anesthetics are available only if prescribed); (2) time to apply the topical anesthetics while waiting for injection to be administered (wait times vary between clinics); and (3) feasibility of parental education. Therefore, helping parents plan for and advocate for proper pain management ahead of time (eg, prescriptions for topical anesthetics when availability in some geographical regions is limited and educating parents), is critical for its implementation in practice.
There is concern that concomitant use of topical anesthetics during vaccination may lead to inactivation of the vaccines or impair absorption due to its antimicrobial activity.100–103 No interference by topical local anesthetics were detected with the DPTaP-IPV-Hib, hepatitis B, or Measles-Mumps-Rubella vaccines in any of the trials that were included in this review (Table 5).43,44,46 The data are consistent with studies performed in adults undergoing Bacille-Calmette-Guérin vaccine administration.83 It is not clear whether these results with topical anesthetics can be generalized to other vaccine antigens; we suggest that testing for interactions between topical local anesthetics should be incorporated in trials evaluating new vaccine antigens.
The use of topical anesthetics was associated with transient local skin reactions such as pallor and erythema.
We found sufficient evidence of benefit from sucrose to reduce pain response during vaccination.23,35,52–58,60–62,64–69 The majority of studies used sucrose in the concentration of 20% to 33% with a typical volume of 2 mL.35,55–58,61,62,67,69 The sucrose concentrations used ranged from 12% to 75%. Also sucrose was administered 2 minutes before the procedure in majority of the studies.23,35,52,53,55–58,61,62,64–67,69
Our finding of a beneficial effect of sucrose for vaccine injection pain is consistent with results of studies involving other invasive skin-breaking procedures performed in neonates and young infants such as heel lance and venipuncture.104 The mechanism of action of sucrose is believed to include release of endogenous opioids and distraction.105
A subgroup analysis based on the concentration of sucrose demonstrated a consistent benefit of concentrations of 50% or 75% across all indicators of infant distress, whereas the results were mixed with concentrations between 20% and 33%. Sucrose in the concentration of 12% was not effective in reducing any of the distress indicators. On the basis of this analysis, sucrose in the dose of 2 mL with concentrations >20% should be used for vaccine injection pain.
Adverse events from sweet-tasting solutions such as coughing and gagging were reported in only 1 trial,58 whereas no episodes of choking or any other adverse events were reported in 2 other trials.60,64 None of these adverse events were clinically significant, as all infants recovered spontaneously within 10 seconds. More consistent documentation of the presence or absence of adverse events is recommended in future research.
The effectiveness of glucose was mixed and not as robust as sucrose. Sucrose should be the preferred sweet-tasting solution, however, if not available glucose should be considered as an alternative. Glucose solution for intravenous administration is easily available in clinical practice in resource-limited countries and is a practical alternative to sucrose for pain management. In settings where sweet-tasting solutions are not available, they can be prepared by using 1 packet of table sugar mixed with 2 teaspoonfuls of clean/sterile water; however, attention needs to be paid to the use of clean/sterile water.
Vapocoolants are volatile liquids that when applied on the skin provides transient anesthesia secondary to evaporation-induced skin cooling.106 The cold sensation may reduce pain by gating pain signals so that cold is experienced rather than pain. The other proposed mechanism is that they decrease the velocity of nerve impulse transmission across nerve fibers.107 As vapocoolants cause cooling and/or burning sensations on the skin, it can be uncomfortable for some individuals including children who may perceive it as a noxious stimulus.8
On the basis of the lack of evidence of benefit, vapocoolants cannot be recommended for use in infants and children. In a single study in adult population, vapocoolants were effective in reducing pain associated with vaccine injection.80 Vapocoolants are an attractive alternative to topical anesthetics due to the short application time (s). However, their application may be associated with discomfort because of the cold sensation that may be perceived as painful. In the included study, there was no report of discomfort from vapocoolant application. In a recent systematic review on venipuncture pain, the pain relief provided by vapocoolants was offset by the pain of their application.108 As the cold sensation may be perceived differently among individuals, their preferences should be taken into consideration when offering vapocoolants.
No trials that evaluated oral analgesics (acetaminophen or ibuprofen) for vaccination pain were identified. Evidence from other needle procedures showed no benefit of either acetaminophen or ibuprofen.81,82 More concerning is the recent data on the effect of prophylactic acetaminophen on immune response study to vaccination.86,88 The use of prophylactic paracetamol was associated with reduction in antibody levels for several vaccines evaluated including hepatitis B, DTPa+HBV+IPV/Hib, and PHiD-CV.86,88 No data on the effect of prophylactic ibuprofen on immune response was identified. Oral analgesics contain sweet-tasting solutions as flavoring agents and individuals may wish to offer them for use before vaccinations; however, sweet-tasting solutions such as sucrose and glucose should be offered instead because of the potential to interfere with the vaccine response.
Two Versus One Intervention
There was evidence of a benefit of the combination of topical anesthetics and breastfeeding.42 There were no additive benefits of combining glucose and pacifier73 or breastfeeding and sucrose.35 These data are limited to single studies with small sample sizes. In previous studies in neonates, the combination of sucrose and pacifiers has been shown to work better than either alone.109
Strengths, Limitations, and Future Research
The major strength of this review is the availability of large evidence base for some of the included interventions (eg, breastfeeding, topical anesthetics in children, and sweet-tasting solutions) and methodological rigor in terms of blinding and quality of included studies. This results in more confidence in our conclusions. In addition, a meticulous approach that included both the GRADE and Cochrane methodologies was used to conduct this systematic review and meta-analysis.
Methodologic challenges and limitations of this review include the small sample sizes for some of the included interventions (eg, vapocoolants across lifespan, topical anesthetics in adults, and oral analgesics) and limited age range of the participants. Furthermore, many of these trials were published before the Consolidated Standards of Reporting Trials (CONSORT) guidelines110 were adopted. On the basis of our review, areas for future research include: (1) evaluation of the effectiveness of expressed breast milk and bottle feeding (in babies whose parents choose to offer bottle to provide expressed breast milk or formula); (2) evaluation of the effects of topical anesthetics on immune response to newer vaccines across lifespan; (3) studies to identify the optimal dose, concentration, and timing of administration of sweet-tasting solutions; (4) additional studies on vapocoolants to confirm or refute its use in children and adults; and (5) combined interventions compared with single active intervention with the goal to reduce pain experienced to zero.
In summary, breastfeeding, topical anesthetics, and sweet-tasting solutions are effective interventions that can be used in infants, children, and adults to reduce vaccine injection pain. Despite the evidence regarding the effectiveness of these interventions for >20 years, children and adults around the world have not reaped the benefits. Rather than conducting effectiveness/efficacy studies for well-studied, effective interventions, it is time to conduct implementation science research so that the use of these interventions becomes the standard of care in clinical practice globally. Educating our consumers (children, parents, and adults undergoing vaccination) and health care providers is crucial to make these changes. There is some evidence that education of individuals can lead to increased use.111
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pain management; randomized controlled trial; systematic review; vaccination
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