Do Biologics Weaken the Immune System?
How biologics affect immunity, infection risk, and what precautions to take
Quick Answer
Biologics do not "shut off" the immune system the way high-dose steroids do. Instead, they selectively modulate specific inflammatory pathways — blocking TNF-alpha, IL-17, IL-23, or JAK enzymes — while leaving much of the immune system intact. However, this selective suppression does increase the risk of certain infections and requires pre-treatment screening and monitoring.
How Biologics Differ from General Immunosuppression
Traditional immunosuppressants like prednisone or high-dose corticosteroids broadly suppress the immune system, leaving patients vulnerable to a wide range of infections and other complications. Biologics take a more targeted approach — they interfere with one specific protein or receptor that drives inflammation in autoimmune disease.
The result is reduced autoimmune inflammation with a more limited impact on overall immune function. However, because the targeted pathways also play roles in defending against certain pathogens, some infection risk is still elevated.
Infection Risks by Drug Class
TNF Inhibitors
Increase risk of bacterial infections, TB reactivation, and invasive fungal infections. Require TB screening before starting. Serious infections occur in a minority of patients.
JAK Inhibitors
Broadest immunosuppression profile among targeted therapies. Elevated risk of herpes zoster (shingles), serious infections, and opportunistic infections. Shingrix vaccination strongly recommended.
IL-23 / IL-17 Inhibitors
Generally lower infection risk than TNF inhibitors. IL-17 inhibition increases oral candidiasis risk. Use with caution in patients with active IBD (IL-17 inhibitors).
IL-4/IL-13 (Dupixent)
Targeted type 2 pathway blockade — limited impact on innate immunity. Lower infection risk profile than most biologics. Conjunctivitis is the most common adverse effect.
Gut-Selective (Entyvio)
Blocks gut-specific integrin — minimal systemic immunosuppression. Infection risk profile is notably favorable compared to systemic immunosuppressants.
Practical Precautions for Patients on Biologics
- Complete all recommended vaccinations before starting biologic therapy when possible
- Get an annual flu shot (inactivated — not live nasal spray)
- Receive Shingrix if age 50+ or on JAK inhibitor at any age (discuss with prescriber)
- Avoid live vaccines while on most biologics
- Tell your doctor promptly about any signs of infection (fever, chills, persistent cough, wound that won't heal)
- Inform any new healthcare provider that you are on a biologic before procedures
- Do not stop your biologic if you develop a minor infection — consult your prescriber
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📚 Sources & Further Reading
Content developed with reference to leading health organizations, peer-reviewed research, and FDA prescribing information.
Medical Disclaimer: Educational content reviewed by the BiologicHealthPlus Clinical Team. Consult your healthcare provider for personalized advice. Last reviewed: August 2026.