When you’re taking a biologic for rheumatoid arthritis, psoriasis, or inflammatory bowel disease, you’re not just treating inflammation-you’re changing how your immune system works. That’s powerful. But it also means your body is less able to fight off infections. And that’s not a small risk. Studies show people on biologics have more than double the chance of ending up in the hospital because of an infection compared to those on older drugs. The good news? This risk isn’t random. It’s predictable. And with the right steps, you can cut that risk by more than a third.
Why Biologics Raise Infection Risk
Biologics aren’t like regular pills. They’re made from living cells and target specific parts of your immune system-usually the ones that cause swelling and joint damage. But those same parts also help you fight bacteria, viruses, and fungi. When you block them, you leave yourself open. The biggest culprits? TNF inhibitors like adalimumab and infliximab. They make up nearly 7 out of 10 biologic prescriptions. And they carry the highest infection risk. But not all biologics are equal. Ustekinumab and secukinumab, for example, have shown lower rates of serious infections in real-world studies. Even within the same class, dosing matters. Adalimumab at 40mg weekly has lower infection rates than infliximab at standard 5mg/kg doses. Why? Because certolizumab, which lacks a key protein region called the Fc segment, doesn’t trigger as strong an immune response in the lungs.It’s not just the drug. Your age, other illnesses, and even steroids you’re taking change the game. If you’re over 50, your risk goes up 37% every decade. If you’re on more than 10mg of prednisone a day, your infection risk jumps 2.3 times. Diabetes? That adds nearly 90% more risk. Chronic lung disease? It nearly doubles it. These aren’t guesses-they’re numbers from large patient studies published in Clinical Infectious Diseases and the CDC’s own risk models.
Screening Before You Start: What You Need
You don’t just walk in and get your first biologic shot. There’s a checklist. And it’s non-negotiable. Skipping even one step can lead to a life-threatening infection later.First, hepatitis B. It’s silent. Many people don’t know they have it. But if you’re on a biologic and have hidden hepatitis B, it can flare up in 27.6% of cases-sometimes fatally. That’s why you need three tests: HBsAg (active infection), HBsAb (immunity), and HBcAb (past exposure). Even if HBsAg is negative, a positive HBcAb means you need a DNA test to check for hidden virus. The AASLD says 8.7% of people with past exposure still carry the virus in their liver. No screening? That’s how someone gets liver failure after starting Humira.
Second, tuberculosis. The standard test is the IGRA (Interferon-Gamma Release Assay). It’s more accurate than the old skin test. But here’s the debate: some experts argue it overdiagnoses latent TB in low-risk areas. In Alabama, 12.7% of patients tested positive, but only 0.8 cases per 100 patient-years actually turned active. Still, guidelines say test everyone. If you’re positive, you get 9 months of treatment before starting the biologic. One patient on MyTherapy said, “They caught my latent TB. I treated it. Three years later, zero infections.”
Third, other infections. Hepatitis C, HIV, and fungal infections like histoplasmosis are also checked-especially if you’ve lived in or traveled to areas where they’re common. Your doctor should ask about past pneumonia, frequent sinus infections, or even camping in the Midwest. These aren’t random questions. They’re red flags.
Vaccinations: Timing Is Everything
Vaccines are your best defense. But if you get them wrong, they won’t work.Live vaccines-like MMR (measles, mumps, rubella) and varicella (chickenpox)-must be given at least 4 weeks before your first biologic. Why? Because your immune system still needs to be strong enough to respond. If you get them after, they can cause the disease they’re meant to prevent.
Inactivated vaccines-flu, pneumococcal, tetanus, and hepatitis B-can be given 2 weeks before. But they need time to work. For hepatitis B, you need to check your antibody levels after the full series. You need at least 10mIU/mL. If you’re below that, you need more shots. Same with varicella: you need IgG levels above 140mIU/mL. If you don’t, you’re still at risk for shingles.
And don’t forget the shingles shot. Shingrix (the non-live version) is now recommended for everyone over 50, even if you’ve had shingles before. But if you’re on a biologic, you can’t get the old live version (Zostavax). You need Shingrix. And you need it before you start. One patient on HealthUnlocked wrote: “My GI doctor started Stelara without checking my vaccines. I got shingles 4 months later.” That’s preventable.
Who’s at Highest Risk? The Numbers Don’t Lie
Not everyone on biologics gets sick. But some are far more vulnerable.People with chronic kidney disease (stage 3 or worse) have more than double the infection risk. Same with COPD. Diabetes? Your risk jumps nearly 90%. And if you’re on steroids? You’re already at higher risk. Combine all three? You’re in the danger zone.
Age isn’t just a number. It’s a multiplier. Over 65? You’re not just older-you’re more likely to get pneumonia, sepsis, or a urinary tract infection that turns deadly. The CDC’s 2025 risk model includes age, kidney function, glucose levels, and even BMI. AI tools like the Cerner Biologics Safety Algorithm now use 87 variables to predict your personal risk. It’s not science fiction. It’s in use today.
What Goes Wrong in Real Life
The guidelines are clear. But in practice? They’re often missed.A 2023 survey of over 2,000 patients found that 63% reported at least one screening or vaccination step skipped. The top three? Not testing for HBV core antibody (41%), not checking varicella immunity (37%), and not giving pneumococcal vaccine before starting (32%).
Doctors aren’t always to blame. Many community clinics don’t have the systems in place. A 2024 AAMC survey found only 38% of private practices fully follow CDC guidelines. Academic hospitals? 73%. The gap is real. That’s why the CDC’s 17-item checklist matters. When patients get all 17 steps done, infection rates drop by 31.2%.
Documentation is another blind spot. The FDA requires screening records to be kept for 10 years after treatment ends. But CMS audits in 2023 showed 23.7% of clinics failed. If you’re ever hospitalized, they’ll ask for those records. If they’re gone? You’re at risk.
What’s Changing in 2025 and Beyond
The rules are getting stricter-and smarter.In February 2025, the FDA released draft guidance requiring all new biologic labels to include real-world infection data. That means if a drug increases shingles risk by 1.33x, it has to say so. The European Medicines Agency now requires drug makers to submit infection risk plans for every new biologic, especially for older patients and those with diabetes or kidney disease.
There’s also new hope in prevention. A trial called PREVENT-IBD is testing daily valacyclovir in patients starting TNF inhibitors. Early results show a 63% drop in viral infections. That could become standard for people who test negative for chickenpox immunity.
And reimbursement is changing. Starting in 2026, Medicare will tie 15% of biologic payments to whether the patient had full screening and vaccination. That’s going to force clinics to finally get their systems right.
What You Should Do Today
If you’re about to start a biologic-or already on one-here’s your action list:- Ask for your full hepatitis B panel: HBsAg, HBsAb, HBcAb
- Get tested for latent TB with an IGRA, not a skin test
- Review your vaccine history with your doctor. Get Shingrix if you haven’t. Get pneumococcal if you’re over 50 or have lung disease
- Make sure your hepatitis B vaccine series is complete. Get a blood test to confirm immunity (≥10mIU/mL)
- Don’t get live vaccines after starting biologics
- Keep a copy of your screening and vaccination records
Don’t wait for your doctor to bring it up. Bring it yourself. You’re not just managing a disease-you’re protecting your life. And that’s worth the effort.
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