When can the trivalent inactivated influenza vaccine be deferred in a patient with moderate‑to‑severe acute illness?

When to Defer Trivalent Influenza Vaccine

Trivalent inactivated influenza vaccine should be deferred in patients with moderate-to-severe acute illness with or without fever until symptoms resolve. 1

Primary Indication for Deferral

Moderate or severe acute illness (including COVID-19) is a precaution for all influenza vaccines—inactivated, recombinant, and live attenuated formulations. 1 This is consistently stated across all ACIP guidelines from 2013 through 2024-2025.

Key Clinical Distinction

• Mild illness with or without fever is NOT a reason to defer vaccination 1
• Only moderate-to-severe illness warrants deferral 1
• The rationale is to avoid confusing vaccine adverse effects with progression of the underlying illness, not because the vaccine is unsafe during mild illness 1

Additional Situations Requiring Deferral (Not Contraindications)

History of Guillain-Barré Syndrome

• Defer if GBS occurred within 6 weeks of a previous influenza vaccination 1
• This is a precaution, not an absolute contraindication—vaccination may still be appropriate if benefits outweigh risks 1

Immunocompromised Patients (Specific Timing)

For children receiving anti-B cell therapies (rituximab, alemtuzumab):

• Defer for 6 months after the last dose, ideally until B cell recovery is documented 1

For hematopoietic cell transplant recipients:

• Defer until 4-6 months post-transplant 1

For solid organ transplant recipients:

• Defer until 3 months post-transplant (may consider at 1 month during active influenza season) 1

Important Clinical Pitfalls

Do NOT Defer For:

• Mild illness (even with low-grade fever) 1
• Egg allergy (this is no longer a contraindication or reason for deferral) 1
• Current corticosteroid use at any dose—proceed with vaccination immediately 2, 3
• Recent corticosteroid discontinuation—no waiting period required 3

Nasal Congestion (LAIV-Specific)

• If using live attenuated vaccine and nasal congestion might impede delivery to nasopharyngeal mucosa, defer until resolution OR use inactivated vaccine instead 1

Practical Algorithm

1. Assess current illness severity:

   • Mild symptoms (minor URI, low-grade fever) → Proceed with vaccination 1
   • Moderate-to-severe illness → Defer until resolution 1

2. Check for GBS history:

   • GBS >6 weeks after prior flu vaccine → Proceed 1
   • GBS within 6 weeks of prior flu vaccine → Use clinical judgment; consider deferral 1

3. For immunocompromised patients:

   • Follow specific timing guidelines above based on therapy type 1
   • Generally, inactivated vaccine is preferred and can be given despite immunosuppression 1

The overarching principle is that vaccination should not be delayed unnecessarily, as timely protection against influenza outweighs theoretical concerns about reduced immunogenicity in most clinical scenarios. 2, 3