Before Starting an Anti-TNF for Crohn's: Your TB, Hepatitis B, and Vaccine Checklist

Starting an anti-tumor necrosis factor (anti-TNF) biologic such as adalimumab or infliximab is one of the most effective steps many people with Crohn's disease take toward lasting remission. These medications also quiet part of the immune system that normally holds certain dormant infections in check. Because of that, your gastroenterology team runs a specific set of screening tests and updates your vaccines before your first injection or infusion. This checklist explains what tb and hepatitis b screening before biologics involves, why latent tuberculosis and hepatitis B matter, and which vaccines to complete ahead of time so you can start treatment safely and without avoidable delays.

Why Screening Happens Before the First Dose

Anti-TNF drugs block tumor necrosis factor, a signaling protein the body uses to wall off and contain infections such as tuberculosis (TB). The FDA prescribing information for Humira (adalimumab) carries a boxed warning for serious infections, including tuberculosis, and the same warning appears on the Remicade (infliximab) label. Removing that signal can allow a dormant, or latent, infection to wake up and spread. A meta-analysis found that infliximab therapy significantly raises the risk of developing active tuberculosis compared with placebo. Hepatitis B behaves similarly. The Humira label warns that TNF blockers may reactivate hepatitis B virus in chronic carriers, in some cases fatally. Screening before starting anti-TNF finds these hidden infections while your immune defenses are still intact.

The Latent Tuberculosis Check

The tuberculosis workup identifies latent TB infection, meaning TB bacteria are present without active illness. The FDA label instructs clinicians to perform a test for latent TB and, if positive, treat it before starting Humira, and the infliximab label gives the same instruction. Two tests detect prior TB exposure: the interferon-gamma release assay (IGRA), a single blood draw, and the older tuberculin skin test (TST). The CDC notes both are acceptable and that routine use of both together is not recommended. IGRA is often preferred because it is unaffected by prior BCG vaccination. If either test is positive, or if you carry TB risk factors, a chest X-ray helps rule out active disease. The U.S. Preventive Services Task Force supports screening people at increased risk for latent infection. A positive TB test before Humira or any anti-TNF does not cancel your biologic. It means you begin a course of TB treatment first, often a few weeks ahead of your first dose.

The Hepatitis B Serology Panel

Hepatitis B screening uses a three-part blood panel: hepatitis B surface antigen (HBsAg), antibody to hepatitis B core antigen (anti-HBc), and antibody to hepatitis B surface antigen (anti-HBs). The FDA labels direct clinicians to evaluate patients for prior evidence of hepatitis B virus (HBV) infection before starting a TNF blocker. Together these three markers show whether you have an active infection, a past resolved infection, or immunity from vaccination. The 2025 AGA clinical practice guideline recommends screening with HBsAg, anti-HBs, and total anti-HBc before immunosuppressive therapy, followed by HBV DNA testing if HBsAg or anti-HBc comes back positive. A hepatitis B test before infliximab that shows HBsAg positive places you at high risk of reactivation, and the guideline recommends antiviral prophylaxis started before your biologic. People who are HBsAg negative but anti-HBc positive carry a lower reactivation risk and are usually monitored rather than treated up front.

Inactivated Vaccines to Update

Inactivated, or non-live, vaccines are safe to give at any point, including during immunosuppression, so your team tries to bring them up to date first. The ACG preventive care guideline recommends annual inactivated influenza vaccination for all adults with IBD and pneumococcal vaccination for those on immunosuppressive therapy. For pneumococcal protection, the 2023 ACIP recommendation gives adults aged 19 to 64 with immunocompromising conditions either PCV20 alone or PCV15 followed later by PPSV23. The recombinant zoster vaccine (RZV, sold as Shingrix) is also non-live, and the CDC recommends two doses for adults aged 19 and older who are or will be immunosuppressed. Hepatitis B vaccination is advised for anyone lacking immunity, again per the ACG guideline. Getting these vaccines before biologics for Crohn's gives your immune system its best chance to build protection while it can still respond fully.

Live Vaccine Timing Rules

Live vaccines contain weakened but replicating organisms, which can cause infection once the immune system is suppressed. The Crohn's & Colitis Foundation explains that live vaccines are generally not recommended for IBD patients on immune-suppressing medications. Common examples include the measles-mumps-rubella (MMR) vaccine and the varicella (chickenpox) vaccine. If you need one of these, the ideal window is before you begin your anti-TNF, and standard practice is to complete a live vaccine several weeks ahead of immunosuppression. The ACG guideline addresses live vaccination as part of the pre-treatment assessment. Once you are on an anti-TNF, live vaccines are usually deferred, and the Foundation advises confirming that any vaccine is inactivated before you receive it. Reviewing your history now, especially if childhood immunization records are incomplete, prevents a last-minute scramble.

Your Pre-Start Screening Checklist

Work through this table with your gastroenterologist to confirm each item is complete before your first dose, and bring any prior vaccination and TB testing records to the appointment.

Screening item	What it checks	If abnormal
Latent TB test (IGRA or TST)	Dormant tuberculosis infection	Treat TB before the biologic
Chest X-ray if indicated	Active TB in the lungs	Rules out active disease
Hepatitis B panel (HBsAg, anti-HBc, anti-HBs)	Active, past, or vaccine-immune HBV status	Antiviral prophylaxis if HBsAg positive
Influenza and pneumococcal vaccines	Vaccine currency	Update before or during therapy
Hepatitis B and recombinant zoster vaccines	Immunity gaps	Complete series, ideally before starting
Live vaccines such as MMR and varicella	Need for any live vaccine	Give before immunosuppression begins

A quick way to prioritize the vaccine portion at your visit:

• Confirm influenza and pneumococcal vaccines are current
• Ask whether you need hepatitis B and recombinant zoster doses
• Schedule any live vaccines before your start date

Putting the Checklist Into Action

Knowing what to do before starting a biologic does more than satisfy a label requirement. This screening catches the two infections most likely to turn dangerous once TNF is blocked, and it uses the pre-treatment window to build vaccine protection while your immune system can still respond. A positive TB or hepatitis B result rarely means you cannot take an anti-TNF. It usually means a short course of preventive treatment comes first, then your biologic follows. Ask your gastroenterology team for your TB test result, your hepatitis B panel, and a written vaccine plan, and coordinate with your primary care provider so nothing slips through the gaps between offices. Arriving at your first dose with every box checked is the most reliable way to start an anti-TNF for Crohn's on solid footing.