Biologics Safety: Infection Risk, Screening, and Vaccination Guidance for Autoimmune Patients

When you’re taking a biologic for rheumatoid arthritis, psoriasis, or Crohn’s disease, you’re not just managing inflammation-you’re changing how your immune system works. That’s powerful. But it also means you’re more vulnerable to infections. The data doesn’t lie: people on biologics have a 2.1 times higher risk of ending up in the hospital because of an infection compared to those on traditional treatments. And it’s not random. This risk is predictable. It’s manageable. But only if you know exactly what to do-and when.

Why Biologics Increase Infection Risk

Biologics are made from living cells. They’re designed to block specific parts of your immune system-like TNF-alpha, IL-17, or IL-23-that drive autoimmune flare-ups. But those same pathways also help fight off bacteria, viruses, and fungi. When you shut them down, your body loses key defenses. That’s why infections become more common, more serious, and sometimes deadly.

Not all biologics carry the same risk. TNF inhibitors like adalimumab and infliximab are the most widely used-and the riskiest. Studies show they increase serious infection risk by 1.6 to 1.9 times compared to non-TNF biologics like ustekinumab or secukinumab. Even among TNF inhibitors, there are differences: certolizumab pegol has a lower rate of respiratory infections because it lacks a part of the antibody (Fc region) that triggers stronger immune reactions. Meanwhile, IL-17 inhibitors like secukinumab raise the risk of fungal infections like candidiasis. JAK inhibitors like tofacitinib, though not technically biologics, are often grouped with them and carry a 1.33 times higher risk of shingles.

The biggest red flag? Reactivation of old infections. Hepatitis B is the most dangerous. If you’ve had it in the past-even if you never knew it-starting a TNF inhibitor can cause the virus to come back with full force. Without screening and treatment, reactivation happens in nearly 28% of cases. That’s why screening isn’t optional. It’s life-saving.

Essential Screening Before Starting a Biologic

Before you get your first injection or infusion, you need three critical tests:

• HBsAg (Hepatitis B surface antigen)
• HBcAb (Hepatitis B core antibody)
• HBsAb (Hepatitis B surface antibody)

If HBsAg is positive, you have active hepatitis B. You’ll need antiviral treatment before starting any biologic. If HBcAb is positive but HBsAg is negative, you’ve had a past infection. That’s called occult hepatitis B. You still need antiviral prophylaxis-8.7% of these patients reactivate without it. And if you’re HBsAb positive, you’re protected, either from vaccination or past recovery.

You also need a tuberculosis test. The gold standard is the interferon-gamma release assay (IGRA), not the old skin test. IGRA is more accurate and less likely to give false positives from BCG vaccination. But here’s the catch: in low-TB areas like the UK or parts of the US, a positive IGRA doesn’t always mean you have latent TB. Some experts argue we over-screen. Still, the American College of Rheumatology says test everyone. It’s safer to treat a false positive than to miss a real one.

Don’t forget other screenings. Blood tests for HIV, hepatitis C, and sometimes fungal infections like histoplasmosis are needed if you’ve lived in or traveled to high-risk areas. And if you’ve had pneumonia, frequent sinus infections, or unexplained fevers, your doctor should look deeper. Your immune system might already be struggling.

Vaccinations: What to Get, When, and Why

Vaccines are your first line of defense. But timing matters. You can’t just get them anytime. Once you start a biologic, live vaccines become dangerous. That means no more MMR, varicella (chickenpox), or nasal flu spray. If you need them, you have to get them before treatment begins.

Here’s the exact schedule:

1. At least 4 weeks before starting: Live vaccines (MMR, varicella)
2. At least 2 weeks before starting: Inactivated vaccines (flu shot, pneumococcal, hepatitis B, Tdap, HPV)

The flu shot? Get it every year-even if you’re on biologics. It’s safe. The pneumococcal vaccine? You need two types: PCV20 or PCV15 first, then PPSV23 at least 8 weeks later. For shingles, get Shingrix (the non-live, two-dose vaccine) before starting biologics. If you already started, you can still get it-but only if your doctor confirms your immune system isn’t too suppressed.

And don’t assume you’re protected because you had chickenpox as a kid. About 1 in 5 adults lose immunity over time. A blood test for VZV IgG is required. If your level is below 140 mIU/mL, you need Shingrix. I’ve seen patients get shingles months after starting Stelara because no one checked their immunity. It was preventable.

Hepatitis B vaccination is critical too. If you’re not immune, get the full three-dose series before starting treatment. Then check your antibody level. You need at least 10 mIU/mL. If you’re below that, you’ll need a booster.

Who’s at Highest Risk?

Not everyone on biologics gets sick. But some people are far more vulnerable. The biggest risk factors:

• Age over 50: Risk goes up 37% every decade.
• On steroids: Taking more than 10 mg of prednisone daily multiplies your infection risk by 2.3 times.
• Diabetes: Odds of infection rise by 89%.
• Chronic kidney disease: Risk jumps 2.15 times.
• COPD: Nearly 2.5 times higher risk of lung infections.

If you have two or more of these, your risk isn’t just elevated-it’s critical. Your doctor should be extra cautious. Maybe choose a lower-risk biologic. Maybe delay treatment until your blood sugar or lung function improves. Maybe add extra monitoring.

What Patients Are Saying-Real Stories, Real Gaps

Patients aren’t just numbers. They’re people who’ve been burned by gaps in care.

One patient in Manchester told me: “My rheumatologist started me on Humira without checking my HBV status. I got hepatitis B six months later. I almost lost my liver.”

Another wrote on a patient forum: “I got shingles because no one asked if I’d had chickenpox. They just assumed I was immune.”

A 2023 survey of over 2,000 patients found that 63% had at least one screening or vaccination step skipped. The most common misses? Hepatitis B core antibody testing (41%) and varicella immunity checks (37%).

But the good news? When patients get full education-like the CDC’s 12-point checklist-78% report zero serious infections. That’s not luck. That’s protocol.

What You Need to Do Right Now

If you’re about to start a biologic, or you’re already on one and haven’t been screened:

1. Ask for HBsAg, HBcAb, and HBsAb tests. Don’t accept just one or two.
2. Ask for a TB test (IGRA, not PPD).
3. Check your vaccine records. Do you have MMR, varicella, pneumococcal, flu, and hepatitis B?
4. If you’re missing live vaccines, get them now-not after you start treatment.
5. Get your VZV IgG and anti-HBs levels checked. If they’re low, get boosted.
6. Ask your doctor: “Am I on a high-risk biologic? Do I need extra monitoring?”

Keep a copy of your screening results and vaccination records. Share them with every doctor you see-even your dentist. Biologics affect everything.

The Future Is Getting Smarter

New tools are coming. AI models like the Cerner Biologics Safety Algorithm now predict your personal infection risk by analyzing 87 factors-your age, medications, lab values, even your zip code. Some clinics are already using them.

In 2026, CMS will start tying 15% of biologic payments to whether clinics followed safety guidelines. That means hospitals will finally have the incentive to get this right.

But until then, you’re your own best advocate. Don’t wait for your doctor to bring it up. Ask. Push. Demand the checklist. Because the difference between getting sick and staying well isn’t luck. It’s knowing what to ask for.