Do biologics weaken my immune system and leave me open to infections?
Biologics work by damping down a specific overactive part of the immune system that drives IBD inflammation, so they do raise the risk of some infections. They do not destroy your immunity wholesale. Because of this, your team screens you before you start, including a tuberculosis test, and keeps your vaccinations up to date. For most people the benefit of controlling the inflammation outweighs the infection risk, which is managed rather than ignored.
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It is a fair worry. Biologics are designed to act on the immune system, so it makes sense to ask what that means for catching infections.
How they actually work
Biologics do not switch off your whole immune system. They are targeted: each one blocks a specific protein or pathway that drives the inflammation of IBD. The Crohn's & Colitis Foundation puts it plainly: biologics target the immune system, which creates a higher risk of infections (Crohn's & Colitis Foundation). So the effect is real, but it is focused rather than a total shutdown.
The infection risk, in plain terms
Because part of the immune response is dampened, the body is a little less able to fend off some infections. For the biologic infliximab, MedlinePlus warns that it can lower your ability to fend off infection and may let a hidden tuberculosis infection become active (MedlinePlus). That is exactly why screening before you start matters.
How the risk is managed
- Screening before you start: a TB skin or blood test, plus checks for hepatitis B (MedlinePlus; Crohn's & Colitis Foundation).
- Vaccinations are brought up to date before starting where possible (Crohn's & Colitis Foundation).
- Watching for signs: a fever, a persistent cough, night sweats, or unexplained weight loss are reported to your team promptly (MedlinePlus).
For most people, uncontrolled IBD inflammation is the bigger threat, and the infection risk is something the team plans around rather than leaves to chance.