Flu Vaccine Administration in Patients Taking Leflunomide

Vaccine Selection Algorithm

• The Centers for Disease Control and Prevention (CDC) recommends that patients taking leflunomide receive the inactivated influenza vaccine (IIV) annually, as leflunomide causes immunosuppression, making patients ineligible for live attenuated intranasal vaccine (LAIV) 1, 2
• The Advisory Committee on Immunization Practices (ACIP) explicitly contraindicates LAIV in persons with known or suspected immunodeficiency diseases or who are receiving immunosuppressive therapies, including those taking leflunomide 1, 2

Route and Administration

• The vaccine should be administered intramuscularly in the deltoid muscle for adults, with a standard dose of 0.5 mL per dose 3

Expected Immune Response

• Patients on immunosuppressive therapy like leflunomide may develop lower antibody titers compared to healthy adults, but vaccination remains effective in preventing lower respiratory tract complications, hospitalization, and death 5

Timing Considerations

• Ideally, patients should be vaccinated during September or October, and vaccination should continue throughout the influenza season as long as vaccine is available 3

Critical Contraindications to Avoid

• LAIV is absolutely contraindicated in immunosuppressed patients, including those on disease-modifying drugs like leflunomide that cause immunosuppression 1, 2
• The live attenuated virus could potentially cause infection in immunocompromised hosts 2, 6

Common Pitfalls

• Minor illnesses with or without fever do not contraindicate vaccination 7
• While immune response may be reduced, vaccination still provides meaningful protection against severe outcomes, and annual revaccination is necessary as immunity declines within one year 5