CONTEXT:

Treatment options for allergic asthma include allergen avoidance, pharmacotherapy, and allergen immunotherapy.

OBJECTIVES:

Summarize and update current evidence for the efficacy and safety of subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT) in pediatric allergic asthma.

DATA SOURCES:

PubMed, Embase, Cochrane Central Register of Controlled Trials (January 1, 2005, through May 8, 2017), ClinicalTrials.gov, and the US Food and Drug Administration Adverse Event Reporting System. We reevaluated trials from our 2013 systematic review.

STUDY SELECTION:

We included studies with children ≤18 years of age in which researchers reported on prespecified outcomes and had an intervention arm receiving aeroallergen SCIT or SLIT. Only randomized controlled trials (RCTs) were included for efficacy. RCTs and non-RCTs were included for safety outcomes.

DATA EXTRACTION:

Two reviewers extracted data. We included 40 studies (17 SCIT trials, 11 SLIT trials, 8 non-RCTs for SCIT safety, and 4 non-RCTs for SLIT safety).

RESULTS:

We found moderate-strength evidence that SCIT reduces long-term asthma medication use. We found low-strength evidence that SCIT improves asthma-related quality of life and forced expiratory volume in 1 second. There was also low-strength evidence that SLIT improves medication use and forced expiratory volume in 1 second. There was insufficient evidence on asthma symptoms and health care use.

LIMITATIONS:

There were no trials in which researchers evaluated asthma symptoms using a validated tool. Study characteristics and outcomes were reported heterogeneously.

CONCLUSIONS:

In children with allergic asthma, SCIT may reduce long-term asthma medication use. Local and systemic allergic reactions are common, but anaphylaxis is reported rarely.

Asthma is a chronic respiratory disease characterized by lower airway inflammation, bronchial hyperreactivity, and airflow obstruction.1 As of 2015, over 6 million or 8.4% of children in the United States had asthma,2 and approximately half of these cases were attributable to atopy.3 The majority of children with allergic asthma are polysensitized.3 

Treatment options for allergic asthma include allergen avoidance, pharmacotherapy, and allergen immunotherapy (AIT). The goal of AIT is to induce allergen-specific immune tolerance, and it is the only allergic disease–modifying therapy available.4 AIT can be given via a subcutaneous immunotherapy (SCIT) or sublingual immunotherapy (SLIT) route. At this time, there are only 4 US Food and Drug Administration (FDA)–approved SLIT tablets available in the United States (house dust mite [HDM], 5-grass, Timothy grass, and ragweed) for treatment of allergic rhinitis; treatment of asthma is off-label.5 

In preparation for an update to the asthma management guidelines,1 a National Heart, Lung, and Blood Institute (NHLBI) working group identified the efficacy and safety of SCIT and SLIT in asthma management as an important topic for an updated systematic review. Our objective in this review is to provide an update to our previous 2013 systematic review (efficacy outcomes included symptoms and medication use for children with asthma and allergic rhinoconjunctivitis) and summarize the current evidence for the efficacy (symptoms, quality of life [QoL], medication use, health care use, and lung function) and safety of SCIT and SLIT, specifically in pediatric allergic asthma.6 This report is derived from a larger review in which the efficacy and safety of SCIT and SLIT in adults and children with allergic asthma was evaluated, which was commissioned by the US Agency for Healthcare Research and Quality (AHRQ).7 

We developed a protocol for the review with guidance from a technical expert panel and input from representatives from both the AHRQ and the NHLBI. The protocol was registered in PROSPERO (http://www.crd.york.ac.uk/PROSPERO), registration number CRD42016047749, and was posted on the AHRQ Web site (https://effectivehealthcare.ahrq.gov/ehc/products/644/2311/asthma-immunotherapy-protocol-160913.pdf). Detailed methods are available in the full evidence report.7 

We conducted a search of PubMed, Embase, and the Cochrane Central Register of Controlled Trials from January 1, 2005, through May 8, 2017. We requested scientific information packages from industry representatives, searched previous reviews and guidelines,8,11 searched ClinicalTrials.gov, and reviewed the FDA Adverse Event Reporting System. We also reevaluated all of the included studies in our previous 2013 systematic review6 to confirm eligibility for this review.

For the main report, we included studies of patients of any age with diagnosis of allergic asthma. For this review, only studies of children ≤18 years of age in which researchers reported on prespecified outcomes were included. Trials were required to have an intervention arm receiving SCIT or SLIT (tablet or aqueous). We excluded studies on food allergies if aeroallergens were not related to asthma, if the type of allergen was not specified, or if the study population did not report data separately for patients with asthma. Study inclusion was not restricted by language of publication. We included only randomized controlled trials (RCTs) for efficacy and RCTs, observational studies, case series, and case reports in which researchers examined safety.

Abstracts and full-text articles were screened independently by 2 reviewers. Any disagreements regarding inclusion were resolved through discussion, and unresolved conflicts were adjudicated during meetings.

Two reviewers extracted data and assessed risk of bias (ROB). Efficacy outcomes that were graded per our protocol included the following: asthma symptoms as reported by asthma control composite scores, QoL, medication use, health care use, and pulmonary physiology (forced expiratory volume in 1 second [FEV1]). Safety outcomes included anaphylaxis, local effects, systemic effects, and deaths. Details regarding immunotherapy including allergen, formulation, dose, and treatment duration were extracted.

For RCTs, the ROB was assessed by using the Cochrane Collaboration’s tool.12 Overall ROB was graded as low, moderate, or high. For observational trials, ROB was assessed by using the Risk Of Bias In Nonrandomized Trials of Interventions, or ROBINS-I tool,13 and overall ROB was graded as low, medium, or high. For case reports and case series, we used the World Health Organization (WHO) criteria to judge the likelihood that the intervention was causally related (dose and time related) to the observed serious adverse event (AE).14 Following this guidance, we reported causality as certain or probable, likely or possible, unlikely or conditional, unclassified or unassessable, or unclassifiable.

We completed a qualitative synthesis for all questions (Tables 14). We considered meta-analyses but determined that the trials were not sufficiently homogenous for quantitative synthesis because of marked variability in patient characteristics, allergen and dose, trial duration, and outcome definitions.

TABLE 1

SCIT Efficacy Summary

OutcomeNo. Studies, ParticipantsAllergen 
(n Studies)Comparators 
(n Studies)Summary of FindingsSOE
Asthma symptoms — — Unable to draw conclusions. Insufficient 
QoL 2, 57 Dust mite (1), Alternaria (1) SCIT versus pharmacotherapy (2) The SCIT arm improved in both trials. Control arm also improved in 1 trial. In 1 trial, researchers measured difference between arms and found no difference Low SOE that SCIT improves asthma-related QoL 
Quick-relief medication use 2, 70 Dust mite (2) SCIT versus placebo (1) versus control (1) 1 study revealed significant reduction in No. d with salbutamol treatment in the SCIT arm when compared with control. The second study did not reveal any significant difference for either arm Low SOE that SCIT reduces short-term medication use 
Long-term control medication use 4, 300 Dust mite (3), multiple (1) SCIT versus placebo (1) versus pharmacotherapy (1) versus vitamin D + pharmacotherapy (1) versus desensitization vaccine (1) 2 studies revealed significant reductions in medication use for SCIT versus comparator arm. In 1 study, researchers didn’t compare arms, and researchers in 1 study found no difference between arms. 2 studies revealed significant decrease in medicine use for SCIT arm at follow-up compared with baseline but not in the comparator arm Moderate SOE that SCIT reduces long-term medication use 
Systemic corticosteroids 2, 150 Dust mite (1), multiple (1) SCIT versus placebo (1) versus control (1) The study on dust mite revealed significant decrease in No. d with systemic steroid use in the SCIT group when compared with control. The study on multiple allergens revealed no difference between groups Low SOE that SCIT reduces systemic steroid use 
Health care use 2, 161 Dust mite (1), multiple (1) SCIT versus placebo (1) versus pharmacotherapy (1) 1 study in which researchers report increase in clinic visits but do not explain the reason or if study related. The second study revealed no difference Insufficient 
Pulmonary physiology: FEV1 5, 378 Dust mite (3), mold (1), multiple (1) SCIT versus pharmacotherapy (3) versus vitamin D + pharmacotherapy (1) versus control (1) 1 study in which researchers found significant difference in the proportion of patients with improved FEV1 in the SCIT arm when compared with pharmacotherapy. 3 studies revealed no significant difference between arms. Researchers in 1 study reported that 100% of patients in the SCIT arm had FEV1 >80% at follow-up Low SOE that SCIT improves FEV1 
OutcomeNo. Studies, ParticipantsAllergen 
(n Studies)Comparators 
(n Studies)Summary of FindingsSOE
Asthma symptoms — — Unable to draw conclusions. Insufficient 
QoL 2, 57 Dust mite (1), Alternaria (1) SCIT versus pharmacotherapy (2) The SCIT arm improved in both trials. Control arm also improved in 1 trial. In 1 trial, researchers measured difference between arms and found no difference Low SOE that SCIT improves asthma-related QoL 
Quick-relief medication use 2, 70 Dust mite (2) SCIT versus placebo (1) versus control (1) 1 study revealed significant reduction in No. d with salbutamol treatment in the SCIT arm when compared with control. The second study did not reveal any significant difference for either arm Low SOE that SCIT reduces short-term medication use 
Long-term control medication use 4, 300 Dust mite (3), multiple (1) SCIT versus placebo (1) versus pharmacotherapy (1) versus vitamin D + pharmacotherapy (1) versus desensitization vaccine (1) 2 studies revealed significant reductions in medication use for SCIT versus comparator arm. In 1 study, researchers didn’t compare arms, and researchers in 1 study found no difference between arms. 2 studies revealed significant decrease in medicine use for SCIT arm at follow-up compared with baseline but not in the comparator arm Moderate SOE that SCIT reduces long-term medication use 
Systemic corticosteroids 2, 150 Dust mite (1), multiple (1) SCIT versus placebo (1) versus control (1) The study on dust mite revealed significant decrease in No. d with systemic steroid use in the SCIT group when compared with control. The study on multiple allergens revealed no difference between groups Low SOE that SCIT reduces systemic steroid use 
Health care use 2, 161 Dust mite (1), multiple (1) SCIT versus placebo (1) versus pharmacotherapy (1) 1 study in which researchers report increase in clinic visits but do not explain the reason or if study related. The second study revealed no difference Insufficient 
Pulmonary physiology: FEV1 5, 378 Dust mite (3), mold (1), multiple (1) SCIT versus pharmacotherapy (3) versus vitamin D + pharmacotherapy (1) versus control (1) 1 study in which researchers found significant difference in the proportion of patients with improved FEV1 in the SCIT arm when compared with pharmacotherapy. 3 studies revealed no significant difference between arms. Researchers in 1 study reported that 100% of patients in the SCIT arm had FEV1 >80% at follow-up Low SOE that SCIT improves FEV1 

—, not applicable.

TABLE 2

SLIT Efficacy Summary

OutcomeNo. Studies, ParticipantsAllergen (n Studies)Comparators (n Studies)FindingsSOE
Asthma symptoms NA NA NA Insufficient 
QoL NA NA NA Insufficient 
Health care use NA NA NA Insufficient 
Quick-relief medication use 2, 218 Dust mite (2) SLIT versus placebo (2) Neither study revealed a significant difference between arms Low SOE that SLIT does not affect quick-relief asthma medication use 
Long-term control medication use 2, 218 Dust mite (2) SLIT versus placebo (2) Neither study revealed a significant difference between arms Low SOE that SLIT does not affect long-term asthma medication use 
Systemic corticosteroids 1, 110 Dust mite (1) SLIT versus placebo (1) 1 study revealed significant reduction in medication consumption in the SLIT group when compared with placebo Insufficient 
Pulmonary physiology: FEV1 6, 375 Dust mite (5); grass (1) SLIT versus placebo (6) 1 study revealed a significant improvement in FEV1 in SLIT versus placebo. 4 studies revealed no difference between study arms. 3 studies revealed a significant improvement in SLIT arm only Low SOE that SLIT improves FEV1 
OutcomeNo. Studies, ParticipantsAllergen (n Studies)Comparators (n Studies)FindingsSOE
Asthma symptoms NA NA NA Insufficient 
QoL NA NA NA Insufficient 
Health care use NA NA NA Insufficient 
Quick-relief medication use 2, 218 Dust mite (2) SLIT versus placebo (2) Neither study revealed a significant difference between arms Low SOE that SLIT does not affect quick-relief asthma medication use 
Long-term control medication use 2, 218 Dust mite (2) SLIT versus placebo (2) Neither study revealed a significant difference between arms Low SOE that SLIT does not affect long-term asthma medication use 
Systemic corticosteroids 1, 110 Dust mite (1) SLIT versus placebo (1) 1 study revealed significant reduction in medication consumption in the SLIT group when compared with placebo Insufficient 
Pulmonary physiology: FEV1 6, 375 Dust mite (5); grass (1) SLIT versus placebo (6) 1 study revealed a significant improvement in FEV1 in SLIT versus placebo. 4 studies revealed no difference between study arms. 3 studies revealed a significant improvement in SLIT arm only Low SOE that SLIT improves FEV1 

NA, not applicable.

TABLE 3

SCIT Safety Summary

Type of ReactionNo. Studies and DesignAllergen (n Studies)No. AEs or Affected Patients/Total No.Description
Treatment ArmComparator Arm
Local reaction 7 RCTs; Reported as patients Dust mite (7) 0/36 patients; 15/65 patients; 26/97 patients 0/30 patients; 0/50 patients; 0/70 patients Local reaction not specified; Urticaria; Local edema, pruritus, and pain 
5 RCTS; Reported as events Dust mite (2); Grass (1); Dog (1); Mold (1) 793 events/124 patients 262 events/43 patients Redness, swelling, pain 
1 non-RCT; Reported as patients Pollen (1) 1/1 NA Erythema, swelling ≥5 cm 
Systemic reactions      
 General reactions 5 RCTS; Reported as patients Dust mite (4); Multiple allergens (1) 22/132 patients 4/128 patients Unspecified systemic reactions 
2 RCTS; Reported as events Dust mite (1); Mold (1) 46 events/61 patients NR Unspecified systemic reactions 
 Respiratory reactions 6 RCTS; Reported as patients Dust mite (4); Grass (1)
Multiple (1) 13/224 patients 3/217 patients Asthma, cough, dyspnea 
1 RCT; Reported as events Dust mite (4) 14 events/20 patients 8 events/10 patients Asthma, cough, dyspnea 
 Cutaneous reactions 1 RCT; Reported as patients Multiple allergens (1) 8/105 0/137 Skin rash 
 Other reactions 1 RCT; Reported as events Grass (1) 21 events/18 patients 9 events/17 patients Eczema, urticaria, rhinoconjunctivitis 
 General reactions 3 non-RCTs; Reported as patients Multiple allergens (2); Dust mite (1) 37/161; 1/NR 0/52 Unspecified systemic reactions 
2 non-RCTs; 1 reported as patients; 1 reported as events Dust mite (1); Multiple (1) 2/NR; 2/NR; 2 events/NR; 4 events/NR NA Hives, wheezing; Rhinorrhea, ocular itching; Asthma, dyspnea; Congestion, rhinorrhea, sneezing 
Anaphylaxis 4 RCTS Dust mite (3), grass (1) 2/96 0/69 Systemic reactions requiring epinephrine 
1 non-RCT Dust mite (1) 0/67 NA 
Death 5 non-RCTs Dust mite (3); Multiple (3); Pollens (1) 0/NR; 1/1 NA Death; 1 case report of death 
Type of ReactionNo. Studies and DesignAllergen (n Studies)No. AEs or Affected Patients/Total No.Description
Treatment ArmComparator Arm
Local reaction 7 RCTs; Reported as patients Dust mite (7) 0/36 patients; 15/65 patients; 26/97 patients 0/30 patients; 0/50 patients; 0/70 patients Local reaction not specified; Urticaria; Local edema, pruritus, and pain 
5 RCTS; Reported as events Dust mite (2); Grass (1); Dog (1); Mold (1) 793 events/124 patients 262 events/43 patients Redness, swelling, pain 
1 non-RCT; Reported as patients Pollen (1) 1/1 NA Erythema, swelling ≥5 cm 
Systemic reactions      
 General reactions 5 RCTS; Reported as patients Dust mite (4); Multiple allergens (1) 22/132 patients 4/128 patients Unspecified systemic reactions 
2 RCTS; Reported as events Dust mite (1); Mold (1) 46 events/61 patients NR Unspecified systemic reactions 
 Respiratory reactions 6 RCTS; Reported as patients Dust mite (4); Grass (1)
Multiple (1) 13/224 patients 3/217 patients Asthma, cough, dyspnea 
1 RCT; Reported as events Dust mite (4) 14 events/20 patients 8 events/10 patients Asthma, cough, dyspnea 
 Cutaneous reactions 1 RCT; Reported as patients Multiple allergens (1) 8/105 0/137 Skin rash 
 Other reactions 1 RCT; Reported as events Grass (1) 21 events/18 patients 9 events/17 patients Eczema, urticaria, rhinoconjunctivitis 
 General reactions 3 non-RCTs; Reported as patients Multiple allergens (2); Dust mite (1) 37/161; 1/NR 0/52 Unspecified systemic reactions 
2 non-RCTs; 1 reported as patients; 1 reported as events Dust mite (1); Multiple (1) 2/NR; 2/NR; 2 events/NR; 4 events/NR NA Hives, wheezing; Rhinorrhea, ocular itching; Asthma, dyspnea; Congestion, rhinorrhea, sneezing 
Anaphylaxis 4 RCTS Dust mite (3), grass (1) 2/96 0/69 Systemic reactions requiring epinephrine 
1 non-RCT Dust mite (1) 0/67 NA 
Death 5 non-RCTs Dust mite (3); Multiple (3); Pollens (1) 0/NR; 1/1 NA Death; 1 case report of death 

NA, not applicable; NR, not reported.

TABLE 4

Safety Summary SLIT

Type of ReactionNo. Studies and DesignAllergen (n studies)No. AEs or Affected Patients/Total No.Description
Treatment ArmComparator Arm
Local reactions 3 RCTs Grass (1) 35%/20 patients 20%/15 patients Oral itching 
Reported as patients Dust mite (2) 5%/20 patients 6.6%/15 patients Stomach ache 
0/55 0/46 No local AEs 
2 RCTs Dust mite (2) 561 events/108 patients 10 events/73 patients Oral itching, ear itching, stomatitis, throat irritation 
Reported as events 19 events/54 patients 2 events/55 patients Unspecified GI events 
1 non-RCT Dust mite (1) 1 event/1 patient NA Eosinophilic esophagitis 
Reported as patients 
Systemic reactions      
 Respiratory 1 RCTs Multiple (1) 1/46 patients 1/22 patients Worsening asthma 
Reported as patients 
4 RCTs Dust mite (3) 82 events/352 patients 73 events/152 patients Rhinitis and/or asthma, dyspnea 
Reported as events Grass (1) 
 Other 10 RCTs Dust mite (6) 50%–68%/46 patients 32%–46%/22 patients Unspecified AEs 
Reported as patients Multiple (1) 115/236 patients 117/236 patients Headache 
Grass (2) 0/20 patients 6.6%/15 patients No systemic AEs 
Tree (1) 0/200 0/156 
2 non-RCTs Dust mite (2) 3 events/1 patient NA Wheezing 
Reported as events 0 event/39 patients NA No systemic reactions 
Anaphylaxis 3 RCTs Dust mite (2) 0/266 0/183 Anaphylaxis 
Reported as patients Multiple (1) 
1 non-RCT Tree (1) 1/1 NA Anaphylactic shock after overdose 
Reported as patients Dust mite (1) 
Death 1 RCT Grass (1) 0/55 0/50 Death 
Reported as patients 
Type of ReactionNo. Studies and DesignAllergen (n studies)No. AEs or Affected Patients/Total No.Description
Treatment ArmComparator Arm
Local reactions 3 RCTs Grass (1) 35%/20 patients 20%/15 patients Oral itching 
Reported as patients Dust mite (2) 5%/20 patients 6.6%/15 patients Stomach ache 
0/55 0/46 No local AEs 
2 RCTs Dust mite (2) 561 events/108 patients 10 events/73 patients Oral itching, ear itching, stomatitis, throat irritation 
Reported as events 19 events/54 patients 2 events/55 patients Unspecified GI events 
1 non-RCT Dust mite (1) 1 event/1 patient NA Eosinophilic esophagitis 
Reported as patients 
Systemic reactions      
 Respiratory 1 RCTs Multiple (1) 1/46 patients 1/22 patients Worsening asthma 
Reported as patients 
4 RCTs Dust mite (3) 82 events/352 patients 73 events/152 patients Rhinitis and/or asthma, dyspnea 
Reported as events Grass (1) 
 Other 10 RCTs Dust mite (6) 50%–68%/46 patients 32%–46%/22 patients Unspecified AEs 
Reported as patients Multiple (1) 115/236 patients 117/236 patients Headache 
Grass (2) 0/20 patients 6.6%/15 patients No systemic AEs 
Tree (1) 0/200 0/156 
2 non-RCTs Dust mite (2) 3 events/1 patient NA Wheezing 
Reported as events 0 event/39 patients NA No systemic reactions 
Anaphylaxis 3 RCTs Dust mite (2) 0/266 0/183 Anaphylaxis 
Reported as patients Multiple (1) 
1 non-RCT Tree (1) 1/1 NA Anaphylactic shock after overdose 
Reported as patients Dust mite (1) 
Death 1 RCT Grass (1) 0/55 0/50 Death 
Reported as patients 

GI, gastrointestinal; NA, not applicable.

The strength of evidence (SOE) was graded for each outcome as specified in our protocol. We used the grading scheme recommended in the Evidence-based Practice Center Methods Guide.15,16 Five domains were considered when grading the SOE for an outcome: trial limitations (called ROB in this review), directness, consistency, precision, and reporting bias.15 SOE was classified into 1 of 4 grades: (1) high grade (indicating high confidence that the true effect is reflected in the evidence, and further research is unlikely to change our confidence in the estimate of the effect), (2) moderate grade (indicating moderate confidence that the true effect is reflected in the evidence, but further research could change our confidence in the estimate of the effect and may change the estimate), (3) low grade (indicating low confidence that the true effect is reflected in the evidence, and further research is likely to change our confidence in the estimate of the effect and is likely to change the estimate), and (4) insufficient grade (indicating evidence is unavailable, or the body of evidence has unacceptable deficiencies, precluding reaching a conclusion).

In the full report, we identified 91 trials in which researchers addressed SCIT and SLIT. Of these, 40 included children: 17 trials of SCIT, 11 trials of SLIT, 8 non-RCTs for SCIT safety, and 4 non-RCTs for SLIT safety. Trial characteristics are summarized in Supplemental Table 5 and 6.

The efficacy of SCIT was reported in 8 trials that included 644 children aged 5 to 14 years (Supplemental Table 5). Asthma severity was graded as mild to moderate persistent in most trials.17,20 Only 2 trials included those with severe persistent asthma,21,22 and researchers did not specify asthma severity in 1 trial.23 Most authors did not specify the level of asthma control, but in 1 trial, children were considered not well controlled.18 In 5 of the trials, patients were monosensitized and received a single allergen (HDM was evaluated in 4,17,19,20,22,23 mold was evaluated in 118); in 2 trials, polysensitized patients received multiple allergens21,24; and in 1 trial, it was unclear if patients were monosensitized or polysensitized, and these patients were treated with HDM.17 The maintenance-dosing interval varied from biweekly to every 6 weeks, and duration of therapy ranged from 3 months to 3 years. SCIT dosing and dosing units were variable.

There were no trials in which researchers reported on asthma control using a validated tool.

In 2 RCTs including 57 children, authors reported on asthma-specific QoL using a validated tool (Asthma Quality of Life Questionnaire [AQLQ]) (Supplemental Table 7).18,19 Researchers in both trials compared single allergen SCIT (HDM and mold) to pharmacotherapy in children with mild to moderate persistent asthma and found a significant improvement in AQLQ scores in the SCIT arm but no difference between study arms. Although these trials had consistent results, there is low SOE that SCIT improves asthma-related QoL based on 2 small trials with medium and high ROB.

In 2 RCTs of HDM SCIT including 70 children, authors reported on quick-relief medication use (Supplemental Table 8).19,23 One of these revealed a significant decrease in the days of salbutamol used per year over the 3-year trial period in the SCIT arm versus the control arm (results in a figure).23 Researchers in the other trial did not find a difference within arms after 8 months and did not report a comparison between arms.19 These 2 small trials with medium and high ROB had inconsistent and direct results, providing low SOE that SCIT improves quick-relief medication use.

In 4 trials, authors reported on long-term control medication use. Two of these trials (both low ROB) included children with mild to moderate persistent asthma, and researchers found a significant decrease in the dose of inhaled corticosteroids (ICSs) used between treatment and comparator arms.17,20 In 1 of the trials with 88 children, blinded study investigators adjusted controller medications per a protocol based on symptom control every 1 to 3 months and found that the dosage of budesonide in the SCIT arm decreased from 196.7 µg at baseline to 71.3 µg at 3-year follow-up, and the final dosage was significantly lower than the comparator arm, which received a desensitization vaccine (101.3 µg).20 Researchers in the other trial evaluated SCIT ± vitamin D (650 IU per day) versus pharmacotherapy (n = 50); ICS doses were only expressed in a figure, but SCIT + vitamin D had a significantly lower ICS dose than the pharmacotherapy arm. Researchers in this trial also had blinded investigators and patients record their doses of ICSs on daily diary cards that were monitored at each study visit. Authors of both trials also reported that significantly more patients in the SCIT arm discontinued ICS treatment versus the comparator arm (20% and 35% vs 0% for SCIT ± vitamin D versus pharmacotherapy; 29% vs 20% for SCIT versus desensitization vaccine).17,20 Researchers in the remaining 2 trials found a significant decrease in controller medication use in only the SCIT arm at follow-up compared with baseline.19,21 In 1 of these, researchers evaluated HDM SCIT versus pharmacotherapy (n = 41) for 8 months, and noted that at baseline, 7 (33%) patients in the SCIT arm and 4 (20%) in the control arm required ICSs, and at follow-up this decreased to 2 (10%) versus no change, respectively (P value not reported).19 In the final trial, researchers compared multiple-allergen SCIT to placebo in 121 children with moderate to severe asthma for 30 months and found that only patients in the SCIT arm had significantly decreased use of ICSs at follow-up (mean of 21 out of 60 days at baseline and 11.3 out of 60 days at follow-up versus 20 out of 60 days at baseline and 14.7 out of 60 days at follow-up in the SCIT and placebo arms, respectively). There was no difference between arms.21 These 4 trials had low (3 trials) to high (1 trial) ROB and presented inconsistent but direct results. There is moderate SOE that SCIT may improve long-term controller medication use.

In 2 RCTs, researchers evaluated systemic corticosteroid use. In 1 trial, researchers evaluating HDM SCIT in 29 children over 3 years found a significant decrease in the mean number of days of treatment required in the previous year in the SCIT arm versus controls (22 days at baseline decreased to 1 day at follow-up in the SCIT group versus 25 days decreased to 12 days in the control group; P < .01).23 In the other trial, researchers did not find a significant change within or between arms in the number of days of children needing systemic steroids in the previous 60 days between baseline and 30-month follow-up.21 From these 2 small trials in which researchers presented inconsistent but direct results with low and medium ROB, we conclude that there is low SOE that SCIT improves systemic corticosteroid use.

In 2 trials with 161 children, researchers evaluated SCIT and health care use (Supplemental Table 9).21,22 A significant difference in hospitalizations or emergency department (ED) visits was not found in either trial, but researchers in 1 trial of HDM SCIT did note a significant increase in the number of office visits in the SCIT arm versus the pharmacotherapy arm (12.4 vs 17.25 visits in the previous 6 months for pharmacotherapy and SCIT arms, respectively).22 The authors did not provide an explanation for this increase. Although these results are consistent and direct, there are only 2 small trials with low and medium ROB, so we conclude that there is insufficient evidence to draw conclusions.

In 5 trials, researchers evaluated FEV1 in 378 children (Supplemental Table 10).17,19,23,24 Researchers in 1 evaluated multiple-allergen SCIT for 12 months in 242 children and noted that significantly more patients in the SCIT arm versus the pharmacotherapy arm had improvement in their FEV1 (60% vs 19%, P = .0001).24 In another trial of HDM SCIT, authors reported that all patients in the SCIT arm had an FEV1 >80% predicted at 8 month follow-up (19 out of 21 patients had FEV1 >80% at baseline), but comparator arm results were not reported.19 In the remaining 3 trials (2 HDM and 1 mold), researchers found no significant differences between SCIT and comparator arms.17,18,23 In 1 of these (mold), researchers did find a significant increase in both arms.18 Overall, inconsistent results were reported in 5 trials with low to high ROB; therefore, there is low SOE that SCIT improves FEV1.

In 6 RCTs including 392 children aged 5 to 18 years, authors reported on the clinical efficacy of SLIT (Supplemental Table 6).25,30 Asthma severity was graded as mild or mild to moderate persistent in all trials. Control status was only specified in 2 trials; authors of 1 mentioned that patients had controlled symptoms,30 and authors of the other reported that patients had ongoing respiratory symptoms despite ICSs and allergen avoidance.26 Only monosensitized patients were included, and HDM SLIT was evaluated in 5,25,26,28,30 and grass was evaluated in 1 trial.27 Maintenance dosing ranged from daily to 2 days per week for 6 to 18 months, and the maintenance dose was variable between trials.

No authors reported on asthma control by using a validated tool.

No authors reported on asthma-related QoL.

In 2 trials in which HDM SLIT (aqueous and tablet) (n = 218) was used, researchers reported on asthma medication use (Supplemental Table 11).25,29 No significant difference between arms for quick-relief or long-term control medication use was found in either trial. In 1 trial, researchers evaluated the use of systemic corticosteroids and did not find any significant difference between arms at follow-up.29 Evidence is low on the basis of only 2 small trials with consistent results and low to medium ROB that SLIT does not reduce quick-relief or long-term control medication use. There is insufficient evidence about the effect of SLIT on systemic corticosteroid use to draw conclusions.

No authors reported on health care use.

Of the 6 trials in which authors reported on FEV1 (5 HDM and 1 grass mix), only 1 revealed a difference between arms at follow-up (Supplemental Table 12). In this trial, researchers evaluated the efficacy of grass SLIT (ultra-rush) for 2 years in 35 children and found a significant improvement in FEV1 percent predicted for SLIT compared with placebo (mean at follow-up = 100.4 vs 88.2 for SLIT and placebo, respectively; P = .005).27 In 3 other HDM SLIT trials, researchers noted a significant improvement in FEV1 at 6-month follow-up compared with baseline in only the SLIT arm (predicted FEV1 of 83.4% at baseline improved to 92.6% at follow-up; P < .001; results for the other trials were presented in a figure).28,30 Overall, there is low SOE that SLIT improves FEV1 on the basis of results from 6 trials with inconsistent results and low to medium ROB.

In our review, we found that local and systemic reactions to both SCIT and SLIT occurred more frequently in the treatment than the comparator arms (Supplemental Tables 13–21). For SCIT, local reactions, including urticaria, swelling, and redness or pain at the injection site, occurred in 0% to 27% of trial patients in the treatment arm or 6.4 events per patient. In the comparator arms, such events occurred in 0% of patients or 0 to 6 events per patient. In the SLIT trials, local reactions, including oral itching, stomatitis, throat irritation, stomach ache, and unspecified GI complaints occurred in 0% to 35% or 0.35 to 5.2 events per patient in the treatment arms versus 0% to 20% or 0.04 to 0.14 events per patient in the comparator arms. There was 1 episode of eosinophilic esophagitis reported in a patient treated with SLIT that resolved after discontinuation of SLIT (non-RCT).

In the SCIT trials, systemic reactions (cough, dyspnea, asthma, hives, rhinoconjunctivitis, eczema, and unspecified reactions) occurred in 6% to 17% or 0.7 to 1.1 events per patient in the treatment arms versus 0% to 3% or 0.5 to 0.8 events per patient in the comparator arms. Anaphylaxis was reported in 2% of patients receiving SCIT in trials (2 of 96 patients) versus no events in the comparator arms (0 of 69 patients). In 1 non-RCT, researchers specifically reported no anaphylactic events in 67 children treated with HDM SCIT. Unspecified systemic reactions were also reported in 23% of patients receiving SCIT in non-RCTs. Other reactions including hives, wheezing, rhinorrhea, asthma, and congestion were also reported in the non-RCTs.

There was 1 case report of death occurring in a 17-year-old girl with moderate persistent asthma who had received SCIT in childhood for 4 years and stopped because of a skin reaction. The authors report that 12 hours after initiation of a new regimen, she complained of abdominal pain, vomiting, and diarrhea without fever. Two days later, she developed acute respiratory failure and was referred to the ICU. She had markedly elevated creatine kinase, elevated troponin, leukopenia, thrombocytopenia, and bilateral interstitial markings on chest radiograph. On day 4, she developed a hypoxic coma leading to intubation and mechanical ventilation, followed by shock and acute renal impairment. By day 5, she developed multiorgan failure and died. The authors considered immunologic mechanisms secondary to manipulation or the way the dose was escalated and considered causality probable. Following WHO criteria for assessing case reports, we also determined that the likelihood of SCIT causing this death (causality) was possible, as the event was related to intervention but was not dose related.31 

In the SLIT trials, systemic reactions (asthma, dyspnea) were rare, occurring in 2% or 0.23 events per patient in the treatment arms versus 4.5% or 0.48 events per patient in the comparator arms. Unspecified adverse reactions occurred in 0% to 68% of patients receiving SLIT versus 0% to 46% in the comparator arms. A researcher in 1 non-RCT described wheezing that occurred 3 times in 1 patient. There was 1 episode of anaphylaxis in 267 patients receiving SLIT. In this case report, a 16-year-old girl with well-controlled intermittent asthma receiving HDM SLIT had 2 episodes of self-resolving wheezing during maintenance therapy, and then in her third year of SLIT, after a 3-week break in maintenance dose, the patient (for unknown reasons) administered herself 60 drops of 100 IR/mL instead of 10 drops and had an episode of anaphylactic shock.32 No deaths were reported for SLIT.

In this systematic review of the evidence for the clinical efficacy and safety of SCIT and SLIT for pediatric allergic asthma, we found moderate-strength evidence that SCIT reduces long-term asthma controller medication use. We otherwise found either low or insufficient evidence for the other outcomes, including asthma-related QoL, quick-relief medication and systemic corticosteroid use (SCIT), asthma-related medication use (SLIT), lung function (FEV1), and health care use. We did not identify any trials in which researchers used validated symptom scales, and therefore we were unable to evaluate this outcome.

In our 2013 systematic review of AIT for pediatric asthma and rhinoconjunctivitis that included 34 trials, we found moderate-strength evidence that SCIT improves asthma symptoms and low-strength evidence that SCIT improves asthma medication scores.33 Unlike this previous review, our search for outcomes relating to asthma symptoms was limited to RCTs in which researchers used validated measurement tools, which we did not find, so we do not have an update for this outcome. Although we did not include medication scores as an outcome, we similarly found that SCIT may decrease medication use.

Our review found that adverse local and systemic reactions to both SCIT and SLIT occurred more frequently in the treatment arms than the comparator arms. Similar to previous reviews, local reactions were commonly reported in both SCIT and SLIT trials. For SCIT, local reactions included urticaria, swelling, redness, or pain at the injection site, and in SLIT trials, local reactions included oral itching and gastrointestinal complaints. Similar to previous reviews, we found rare reports of anaphylaxis associated with SCIT, and although rarely reported, we are including a case report of death associated with SCIT as well as a case report of anaphylactic shock associated with an overdose of HDM SLIT. Per the practice guidelines, AIT should be administered in a setting that can monitor for and manage adverse reactions, and patients should be monitored for 30 minutes after therapy (this includes the first dose of SLIT). After the first dose, SLIT can be administered at home. Patients administering SLIT at home should, however, be instructed on how to manage adverse reactions and situations when SLIT should be held.34 For patients with asthma, AIT should not be given to patients with severe, unstable, or poorly controlled symptoms.11,34 

The trials included in our review were heterogeneous in patient and intervention characteristics and in how outcomes were measured. Because of this heterogeneity, we were only able to synthesize the data qualitatively.

The studies in this review included only children ≤18 years of age. Other studies in the full report included children and adults but did not report the results for children separately; therefore, they could not be used in this review (n = 9). Additional studies that we were not able to include had mixed populations of children with asthma and allergic rhinitis but did not report outcomes separately for those with asthma. Although researchers in several trials reported asthma symptoms as an outcome, we did not find any that reported this outcome by using a validated tool.

Our results are applicable to children and adolescents with allergic asthma due to inhalant allergens. The majority of SCIT trials and all of the SLIT trials used a single allergen (HDM) AIT in monosensitized patients, and it’s possible that results may not be generalizable to patients with allergic asthma who are polysensitized, patients treated with multiple allergens, or other inhalant allergen AIT. Finally, most of the trials included children and adolescents with mild to moderate persistent asthma. Patients with severe, uncontrolled asthma are at increased risk for systemic reactions, therefore AIT should not be initiated unless asthma symptoms are stable.11 

Future researchers should consider evaluating multiple-allergen AIT as well as other inhalant allergens in polysensitized patients. In our review, we did not find studies in which researchers evaluated the effect of single versus multiple-allergen AIT in patients who are polysensitized, which is an important clinical question to address in future trials. We also did not find any trials in which researchers reported asthma symptoms using a validated scale, and we would encourage this in future trials so that this important outcome can be more easily compared across trials. None of the researchers in the efficacy trials directly compared different lengths of treatment or followed patients for an extended period of time after completion of therapy, so the question of how long AIT must be given to see a lasting effect on asthma symptoms remains an important unanswered clinical question. Because there are only 4 FDA-approved SLIT tablets at this time, the use of other sublingual drops or tablets would be considered off-label. There is a need for rigorous trials to evaluate these SLIT products in United States populations.34 

In children with allergic asthma, SCIT may reduce the need for asthma medication, improve FEV1, and improve asthma-related QoL. SLIT may improve FEV1, but does not seem to improve asthma medication use. Local and systemic allergic reactions to SCIT and SLIT are common. Life-threatening events such as anaphylaxis and death were reported rarely.

     
  • AE

    adverse event

  •  
  • AHRQ

    Agency for Healthcare Research and Quality

  •  
  • AIT

    allergen immunotherapy

  •  
  • AQLQ

    asthma quality of life questionnaire

  •  
  • ED

    emergency department

  •  
  • FDA

    US Food and Drug Administration

  •  
  • FEV1

    forced expiratory volume in 1 second

  •  
  • HDM

    house dust mite

  •  
  • ICS

    inhaled corticosteroid

  •  
  • NHLBI

    National Heart, Lung, and Blood Institute

  •  
  • QoL

    quality of life

  •  
  • RCT

    randomized controlled trial

  •  
  • ROB

    risk of bias

  •  
  • SCIT

    subcutaneous immunotherapy

  •  
  • SLIT

    sublingual immunotherapy

  •  
  • SOE

    strength of evidence

  •  
  • WHO

    World Health Organization

Dr Suarez-Cuervo drafted the protocol with contributions by each author, conducted the search, screened studies, developed tables and flowcharts, assisted with drafting the review manuscript, and coordinated contributions from the coauthors; Dr Robinson drafted the protocol with contributions by each author; Dr Rice drafted the initial manuscript and reviewed and revised the manuscript; and all authors assessed studies for inclusion, extracted data, assessed the risk of bias, critically reviewed the manuscript for important intellectual content, approved the final manuscript as submitted, and agree to be accountable for all aspects of the work.

FUNDING: Funded under contract 290-2015-00006I from the Agency for Healthcare Research and Quality (AHRQ) from the US Department of Health and Human Services. The authors of this article are responsible for its content. Statements in the article should not be construed as endorsement by the AHRQ or the US Department of Health and Human Services. The AHRQ retains a license to display, reproduce, and distribute the data and the report from which this article was derived under the terms of the agency’s contract with the author.

This trial is based on research conducted at the Johns Hopkins University Evidence-based Practice Center under contract 290-2015-00006I.

We acknowledge Jessica Gayleard, BS (Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD), who assisted in the screening of search results.

This topic was nominated by the NHLBI and was selected by AHRQ for systematic review by an evidence-based practice clinic. A representative from the AHRQ served as a contracting officer’s technical representative and provided technical assistance during the conduct of the full evidence report and provided comments on draft versions of the full evidence report. The AHRQ did not directly participate in the literature search, determination of trial eligibility criteria, data analysis or interpretation, or preparation, review, or approval of the article for publication.

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Competing Interests

POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose.

FINANCIAL DISCLOSURE: The authors have indicated they have no financial relationships relevant to this article to disclose.

Supplementary data