Flu Vaccine Administration in Patients Taking Leflunomide
Patients taking leflunomide should receive the inactivated influenza vaccine (IIV) annually, not the live attenuated intranasal vaccine (LAIV), due to their immunosuppressed state from this disease-modifying antirheumatic drug.
Vaccine Selection Algorithm
Use Inactivated Influenza Vaccine (IIV)
- Leflunomide causes immunosuppression, making patients ineligible for LAIV 1
- The ACIP explicitly contraindicates LAIV in persons with "known or suspected immunodeficiency diseases or who are receiving immunosuppressive therapies" 1
- Inactivated vaccines are safe and appropriate for immunosuppressed patients, as they cannot cause infection 2, 3
Route and Administration
- Administer IIV intramuscularly in the deltoid muscle for adults 4
- Standard dose: 0.5 mL per dose for adults 4
- No special timing considerations relative to leflunomide dosing are required 5
Expected Immune Response
Reduced but Meaningful Protection
- Patients on immunosuppressive therapy like leflunomide may develop lower antibody titers compared to healthy adults 1, 6
- Despite potentially suboptimal serologic response, vaccination remains the only proven method for preventing influenza infection 6
- Even with reduced antibody response, the vaccine effectively prevents lower respiratory tract complications, hospitalization, and death 1
Timing Considerations
Optimal Vaccination Window
- Ideally vaccinate during September or October 4
- Continue vaccination throughout the influenza season as long as vaccine is available 4
- No specific requirement to time vaccination between leflunomide doses, unlike chemotherapy where between-cycle timing may optimize response 6
Critical Contraindications to Avoid
Never Use LAIV (FluMist)
- LAIV is absolutely contraindicated in immunosuppressed patients 1
- This includes patients on disease-modifying drugs like leflunomide that cause immunosuppression 1
- The live attenuated virus could potentially cause infection in immunocompromised hosts 1
Common Pitfalls
Do Not Delay Vaccination
- Avoid unnecessarily deferring vaccination due to concerns about immunosuppression 6
- The benefit of any protection outweighs the risk of no vaccination 6
- Minor illnesses with or without fever do not contraindicate vaccination 7
Do Not Assume Vaccination is Futile
- While immune response may be reduced, vaccination still provides meaningful protection against severe outcomes 1, 6
- Influenza infection can cause significant additional morbidity in immunosuppressed patients 6