When you start a biologic for rheumatoid arthritis, psoriasis, or Crohn’s disease, you’re not just getting a powerful drug-you’re stepping into a new risk landscape. These medications, from adalimumab to ustekinumab, work by calming your overactive immune system. That’s great for stopping joint damage or skin flares. But it also leaves you more vulnerable to infections that your body would normally fight off easily. The data is clear: people on biologics have more than double the risk of serious infections that land them in the hospital compared to those on older treatments. And it’s not just a theoretical concern-it happens in real time, in real people.
Why Biologics Increase Infection Risk
Biologics don’t just turn down the immune system-they target specific parts of it. TNF inhibitors like adalimumab and infliximab block a key protein (tumor necrosis factor) that helps your body fight off bacteria and fungi. That’s why these drugs carry the highest infection risk among biologics. Studies show patients on TNF inhibitors have a 1.6 to 1.9 times higher chance of serious infections than those on non-TNF biologics like ustekinumab or secukinumab. Even within the TNF class, differences matter: infliximab has a 22% higher infection risk than adalimumab in psoriasis patients. Certolizumab pegol, which lacks a certain protein structure (Fc region), shows lower rates of respiratory infections. It’s not one-size-fits-all.The biggest threat isn’t just common colds. It’s tuberculosis, hepatitis B reactivation, fungal infections, and serious pneumonia. In fact, nearly 44% of all serious infections in biologic users are respiratory-sinus infections, bronchitis, pneumonia. And if you’re over 50, have diabetes, chronic lung disease, or are taking more than 10 mg of prednisone daily, your risk jumps even higher. One study found that patients on high-dose steroids while on biologics had more than double the infection risk compared to those not on steroids.
Screening Before You Start: What’s Required
Before you get your first biologic shot or infusion, you need a full infection risk check. This isn’t optional. It’s standard, and it’s life-saving. The American College of Rheumatology and CDC agree: three tests are non-negotiable for everyone.- HBV screening: You need three blood tests-HBsAg, HBsAb, and HBcAb. Why? Because up to 4.3% of autoimmune patients carry hidden hepatitis B. If you’re HBcAb positive and you start a TNF inhibitor without treatment, your chance of full-blown hepatitis B reactivation is 27.6%. That’s not a small number. It’s deadly. If your HBcAb is positive, you’ll need a DNA test to check for hidden virus, and you’ll likely need antiviral medication before and during biologic therapy.
- TB screening: You’ll get either a skin test (TST) or a blood test (IGRA). The IGRA is more accurate, with 98% specificity. But here’s the catch: in low-TB areas like Australia or the U.S. Midwest, positive IGRA results don’t always mean active disease. Some experts argue we’re over-testing, but skipping it is dangerous. If latent TB is found, you’ll need 9 months of treatment before starting your biologic.
- COVID-19, flu, and other active infections: If you have a fever, cough, or active infection, your biologic will be delayed. It’s not just about feeling sick-it’s about giving your body a chance to recover before suppressing your defenses.
Missing one of these tests isn’t a minor oversight. It’s a known cause of preventable hospitalizations. Patient forums are full of stories like: “My GI doctor started me on Stelara without checking my vaccine history-I got shingles four months later.” That’s preventable.
Vaccinations: Timing Is Everything
Vaccines are your first line of defense-but only if they’re given at the right time. Once you start a biologic, live vaccines become dangerous. That means no more MMR, varicella (chickenpox), or nasal flu spray after your first dose.You need to get all your live vaccines at least 4 weeks before starting your biologic. Inactivated vaccines like flu, pneumococcal, and hepatitis B can be given 2 weeks before, but ideally, they’re done even earlier. Here’s what you need:
- Shingrix (shingles vaccine): Two doses, 2-6 months apart. Must be completed before starting biologics. If you’re over 50 and haven’t had it, this is critical-biologics increase your shingles risk by 1.5 to 2 times.
- Pneumococcal vaccines: PCV20 or PCV15 + PPSV23. These protect against pneumonia. You need both if you haven’t had them before.
- Influenza vaccine: Get the shot every year. No nasal spray. The shot is safe and effective.
- Hepatitis B vaccine: If you’re not immune (anti-HBs <10 mIU/mL), you need the full 3-dose series. Check your levels after the last shot-you need at least 10 mIU/mL to be protected.
- Varicella IgG: If you’re not sure if you had chickenpox or the vaccine, get tested. If your IgG is below 140 mIU/mL, you need the vaccine before starting.
One patient in Melbourne shared: “I got my Shingrix and pneumococcal shots 6 weeks before my first Humira. I’ve been on it for 3 years. Zero infections.” That’s the goal.
How Risk Varies by Biologic Type
Not all biologics are equal when it comes to infection risk. Here’s a quick breakdown:| Biologic Class | Examples | Key Infection Risks | Relative Risk vs. Non-TNF |
|---|---|---|---|
| TNF inhibitors | Adalimumab, Infliximab, Etanercept | TB reactivation, fungal infections, pneumonia | 1.6-1.9x higher |
| IL-12/23 inhibitors | Ustekinumab | Lower overall risk; safer in HBV carriers | ~1.2x higher (not significant) |
| IL-17 inhibitors | Secukinumab, Ixekizumab | Candidiasis (oral, genital yeast) | 1.4x higher for yeast infections |
| JAK inhibitors | Tofacitinib, Baricitinib | Herpes zoster (shingles), blood clots | 1.33x higher for shingles |
For someone with hepatitis B, ustekinumab is often the safer choice. For someone with a history of recurrent yeast infections, IL-17 inhibitors might not be ideal. Your doctor should pick the right one based on your history-not just your diagnosis.
What Happens After You Start?
Screening and vaccines don’t end after your first dose. You need to stay alert.- Watch for fever, night sweats, unexplained weight loss, or persistent cough-signs of TB or fungal infection.
- Report any skin rashes, mouth sores, or genital itching immediately-they could be early signs of candidiasis or shingles.
- Get a flu shot every year, even if you’ve had one before. Immunity fades.
- Don’t skip your annual blood tests. Your doctor should check liver function, CBC, and sometimes HBV DNA if you’re a carrier.
Patients who follow the CDC’s 12-point infection prevention checklist are 78% less likely to have a serious infection. That’s not a small difference. That’s life-changing.
What’s Changing in 2025?
New guidelines are coming fast. In February 2025, the FDA proposed requiring real-world evidence of infection risk reduction for any new biologic label expansion. That means drug companies will have to prove their drugs don’t cause more infections than older ones.AI tools are now being used to predict risk. The Cerner Biologics Safety Algorithm, validated in 2023, uses 87 clinical factors-your age, meds, lab values, even your zip code-to give you a personalized infection risk score. It’s not perfect, but it’s helping doctors make smarter choices.
By 2026, Medicare will start tying 15% of biologic payments to whether clinics followed infection prevention protocols. That’s going to change how clinics operate. You’ll see more structured checklists, better vaccine tracking, and fewer missed screenings.
What You Can Do Today
You don’t have to wait for your doctor to bring this up. Take control.- Request your full infection screening history-ask for copies of your HBV and TB test results.
- Check your vaccine record. Do you have Shingrix? Pneumococcal? Hepatitis B? If you’re unsure, get tested.
- If you’re overdue on any vaccine, schedule it now-not after your biologic starts.
- Ask your doctor: “Which biologic do you recommend for me, and why? What’s my specific infection risk based on my health history?”
- Keep a personal log: dates of vaccines, screening results, and any infections you’ve had since starting treatment.
The goal isn’t to scare you. It’s to arm you. Biologics can change your life-for the better. But only if you and your care team treat infection risk like the serious, preventable threat it is. You’re not just taking a drug. You’re managing your immune system. And that requires a plan.
Can I get the flu shot while on biologics?
Yes, you can and should get the flu shot every year while on biologics. But only the inactivated (injected) version. The nasal spray flu vaccine contains live virus and is unsafe for people on immune-suppressing drugs. The shot is safe, effective, and recommended by the CDC for all biologic users.
What if I already started a biologic and never got vaccinated?
If you’ve already started, live vaccines (like MMR or varicella) are no longer safe to give. But you can still get inactivated vaccines like flu, pneumococcal, and hepatitis B. Talk to your doctor about your vaccination history. Even if you’re late, getting these shots now still reduces your risk. You won’t get the same level of protection as if you’d been vaccinated beforehand, but it’s better than nothing.
Are biologics safe if I’ve had hepatitis B in the past?
Yes-but only with careful management. If you’ve had hepatitis B, you must be screened for hidden virus (HBcAb, HBV DNA). If you’re a carrier, you’ll need antiviral medication (like entecavir or tenofovir) before and during your biologic treatment. TNF inhibitors carry a 27.6% risk of reactivating hepatitis B without this protection. Ustekinumab is often preferred in this group because it has a much lower reactivation risk-just 1.2%.
Why do I need to wait 4 weeks after a live vaccine before starting a biologic?
Live vaccines contain weakened forms of the virus. Your immune system needs time to build a strong response without being suppressed. If you start a biologic too soon, your body won’t develop proper immunity-and you could get sick from the vaccine itself. Waiting 4 weeks gives your immune system the best chance to respond fully before the biologic begins to dampen its activity.
What if I live in a rural area and my doctor doesn’t follow the guidelines?
You’re not alone. In rural areas, only 28% of patients get all required screenings before starting biologics. If your clinic doesn’t follow CDC or ACR guidelines, ask for a referral to a rheumatology or gastroenterology center that does. Many academic hospitals offer telehealth consultations for pre-biologic screening. You can also request your records and take them to a specialist for review. Your safety is worth the extra step.
Can I travel while on biologics?
Yes, but plan ahead. Avoid areas with high rates of TB, fungal infections (like histoplasmosis in the Ohio River Valley), or poor sanitation. Make sure your vaccines are up to date before you go. Carry a letter from your doctor explaining your treatment in case you need medical care abroad. Avoid raw or undercooked food, and be extra careful about hand hygiene. Travel increases exposure risk-so preparation is key.
Next Steps for Patients
Start by gathering your medical records. Call your doctor’s office and ask for copies of your HBV, TB, and vaccination history. If you’re missing anything, schedule the tests now. Don’t wait for your next appointment. If you’re unsure about your vaccine status, get a blood test for varicella and hepatitis B immunity. Ask your doctor which biologic they’re recommending-and why. Then, ask: “What’s my personal infection risk, and how are we minimizing it?”Biologics are powerful. They can give you back your life. But they’re not magic. They require responsibility, planning, and partnership with your care team. The best outcomes don’t come from luck-they come from doing the right things, at the right time, every time.