Biologic Therapy Infection Risks: What You Need to Know

When you take biologic therapy, a targeted treatment that blocks specific parts of the immune system to reduce inflammation in conditions like rheumatoid arthritis, Crohn’s disease, or psoriasis. Also known as biologics, these drugs work differently than traditional pills—they’re made from living cells and zero in on the exact proteins driving your immune system’s overreaction. But this precision comes with a trade-off: by calming your immune response, you also make it harder for your body to fight off infections.

That’s why infection risks, the increased chance of getting bacterial, viral, or fungal infections while on biologic therapy are one of the most serious concerns for patients and doctors. Studies show people on biologics are 2 to 3 times more likely to get serious infections like pneumonia, tuberculosis, or skin abscesses. Some infections, like hepatitis B or fungal infections in the lungs, can hide quietly and flare up dangerously once treatment starts. Even minor cuts or insect bites can turn into big problems if your immune system is suppressed.

Not all biologics carry the same level of risk. TNF inhibitors, a common class of biologics that block tumor necrosis factor, a key inflammation driver—like adalimumab or infliximab—are linked to the highest infection rates, especially for tuberculosis. Other types, like IL-17 or IL-23 blockers, might be safer for some patients, but they still carry warnings. Your doctor will test you for latent TB, hepatitis, and other hidden infections before starting you on any biologic. Vaccines are crucial too—you need them before treatment begins, because once you’re on biologics, live vaccines become unsafe.

It’s not just about avoiding sickness—it’s about recognizing it fast. A low-grade fever, unusual fatigue, or a sore throat that won’t go away might not seem like much, but they could be early signs of something serious. If you’re on biologic therapy, you need to treat every infection like a red flag. Don’t wait. Call your doctor. Early antibiotics or antivirals can make all the difference.

Many people worry about these risks and stop their meds. But for most, the benefits outweigh the dangers—especially when you’re monitored closely. The goal isn’t to avoid biologics entirely, but to use them smartly. Regular blood tests, good hygiene, avoiding sick people in flu season, and knowing your body’s warning signs are your best defenses. This collection of posts covers everything from how biologics interact with other drugs, to real-life stories of patients managing infections, to what your pharmacist needs to know when you’re on these treatments. You’ll find practical advice on spotting trouble early, protecting yourself without living in fear, and making informed choices with your care team.