What is the role of allergen immunotherapy (the vaccine-like approach) in the treatment of allergic rhinitis?

Role of Allergen Immunotherapy for Allergic Rhinitis

Allergen immunotherapy (AIT) should be offered or referred to patients with allergic rhinitis when symptoms remain inadequately controlled despite pharmacologic therapy and allergen avoidance, or when patients prefer disease-modifying treatment. 1, 2

Why Consider Immunotherapy

AIT is the only disease-modifying treatment for allergic rhinitis that can alter the natural course of the disease 3, 4, 5. Unlike medications that only suppress symptoms, immunotherapy induces immune tolerance through regulatory T-cell induction and protective IgG antibody production 6, 5.

Key Benefits Beyond Symptom Control

• Sustained effects: Clinical benefits persist for years after treatment discontinuation 3, 7
• Prevents asthma development: Reduces risk of progression from allergic rhinitis to asthma 3, 2
• Prevents new sensitizations: May stop development of additional allergen sensitivities 3
• Long-term cost-effectiveness: Despite higher initial costs, becomes cost-effective compared to continuous pharmacotherapy 3, 7

When to Recommend Immunotherapy

The 2024 clinical practice guideline provides clear indications 1:

Primary Candidates

• Patients with inadequate symptom control despite intranasal corticosteroids and antihistamines
• Those experiencing unacceptable medication side effects
• Patients wishing to avoid long-term pharmacotherapy
• Those with demonstrable IgE antibodies to clinically relevant allergens confirmed by testing 3, 4, 2

Important Qualification

Do not offer immunotherapy to patients with negative IgE testing or positive tests that don't correlate with clinical symptoms and exposure 8. The presence of specific IgE alone does not indicate clinical sensitivity.

Treatment Options

Two FDA-approved forms exist in the United States 2, 9:

Subcutaneous Immunotherapy (SCIT)

• Administered in physician's office
• Requires approximately 18 injections on average 10
• Systemic reaction rate: 0.06-0.9% 2
• Death rate: 1 per 2.5 million injections 2
• Strong evidence base from systematic reviews 11

Sublingual Immunotherapy (SLIT)

• FDA-approved tablets for grass, ragweed, house dust mites, birch-homologous trees, and Japanese cedar 9
• Self-administered at home after first dose observation
• Lower anaphylaxis risk than SCIT 5
• Similar efficacy to SCIT 5

Evidence of Effectiveness

Meta-analysis of 51 trials with 2,871 participants demonstrated 11:

• Symptom score reduction: SMD -0.73 (95% CI -0.97 to -0.50, P < 0.00001)
• Medication use reduction: SMD -0.57 (95% CI -0.82 to -0.33, P < 0.00001)

Safety Considerations

Critical requirement: The clinician performing allergy testing or administering AIT must be able to diagnose and manage anaphylaxis 1. This is a strong recommendation.

Adverse Event Profile

From analysis of 4,723 injections 10:

• Systemic reactions occurred in 21% of patients after 1.29% of injections
• Most reactions were late-onset (>30 minutes) and included dyspnea, rhinorrhea, fever, fatigue, urticaria
• Higher reaction rates during up-dosing phase and with grass pollen versus house dust mite
• Adrenaline required in 0.13% of active treatment injections 11
• No fatalities in reviewed studies 11

Contraindications

• Severe, uncontrolled asthma
• Significant or unstable cardiovascular disease
• Concurrent β-adrenergic blocker use (relative contraindication—makes reactions harder to treat) 3

Treatment Duration and Monitoring

• Expect improvement: After reaching maintenance dose 3
• Reassess at 1 year: If no improvement after 1 year of maintenance treatment, review and consider discontinuation 3
• Typical duration: Continue for 3 years or longer if effective 3
• No specific biomarkers: Currently cannot predict which patients will maintain long-term remission after stopping 3

Common Pitfalls to Avoid

1. Don't initiate immunotherapy without confirmed IgE-mediated disease: Testing must correlate with clinical symptoms and exposure patterns 8, 3
2. Don't use immunotherapy as first-line treatment: It's indicated when pharmacotherapy is inadequate, not as initial therapy 12, 2
3. Don't administer without anaphylaxis preparedness: Emergency equipment and trained personnel are mandatory 1
4. Don't continue ineffective treatment: Reassess after 1 year of maintenance dosing 3

Integration with Pharmacotherapy

The 2017 Joint Task Force guideline establishes the pharmacotherapy hierarchy 12:

• First-line: Intranasal corticosteroids (monotherapy)
• Second consideration: Adding intranasal antihistamine for moderate-to-severe disease
• Immunotherapy consideration: When above approaches fail or patient prefers disease modification

Immunotherapy is not a replacement for acute symptom management but rather a disease-modifying intervention for long-term control 12, 2.