Biologics used for ankylosing spondylitis can raise the chance of infection because they calm the immune system that drives inflammation. Most infections are treatable, but some can be serious, and infections such as tuberculosis may become active again after being silent. Doctors lower risk by screening before treatment, reviewing vaccines and other medicines, and monitoring symptoms. Your risk depends on the drug and your health.
Why can biologics increase infection risk?
Ankylosing spondylitis is an inflammatory condition that mainly affects the spine and the joints connecting the spine to the pelvis. Biologic medicines target specific parts of the immune system that contribute to inflammation. By reducing this activity, they can relieve symptoms and help control the disease. However, the same immune pathways also help the body defend itself against infections.
Two main groups of biologics used for ankylosing spondylitis are tumor necrosis factor (TNF) inhibitors and interleukin-17 (IL-17) inhibitors. TNF inhibitors include medicines such as adalimumab, etanercept, infliximab and golimumab. IL-17 inhibitors include secukinumab and ixekizumab. The medicines work differently, so their safety considerations are not identical. The ASAS-EULAR recommendations for axial spondyloarthritis identify TNF and IL-17 inhibitors as important treatment options, with treatment choices guided by a person's disease and other health needs.
How much does the risk of infection increase?
Biologic treatment can increase the likelihood of certain infections, but there is no single percentage that accurately describes the risk for everyone with ankylosing spondylitis. The chance of infection depends on the medicine, medical history, age and other treatments being taken. Some infections are mild and resolve with routine care, while others can become serious and require hospital treatment.
Risk may be higher in older adults, people who have frequent or serious infections, and those who take other medicines that suppress the immune system, particularly corticosteroids or additional disease-modifying drugs. The Arthritis Foundation's guidance on biologic medicines notes these concerns for people receiving TNF blockers, including increased infection risk during the first months of treatment. A history of infection does not automatically rule out biologic treatment, but it is important information when choosing and monitoring a medicine.
Which infections are most important to know about?
Common infections
People receiving biologics may develop infections affecting the upper respiratory tract, skin or urinary tract. Examples include a sore throat, a respiratory infection, a painful skin infection or a urinary tract infection. Some medicines may also increase the risk of certain viral or fungal infections. These problems do not always become serious, but prompt attention can help prevent complications.
Tell your healthcare team about infections that keep returning, take longer than expected to improve, or appear to be getting worse. Do not assume that a persistent cough, unusual fatigue or a skin problem is simply an ordinary side effect of treatment.
Tuberculosis: an infection that can become active again
Tuberculosis (TB) deserves particular attention because a person can carry the bacteria without feeling ill. This is called latent TB. When immune defenses are reduced, latent TB may become active disease. Active TB can affect the lungs and may cause a persistent cough, fever, night sweats or unexplained weight loss.
TNF inhibitors are particularly associated with TB reactivation, although TB screening is also important before treatment with other biologic medicines. The U.S. National Library of Medicine's MedlinePlus information on adalimumab warns that the medicine may allow an existing TB infection to become more serious. Tell the prescriber if you have previously had TB, received treatment for it, lived in an area where TB is common, or had close contact with someone with TB.
Hepatitis B and other infections that may remain hidden
Some infections can be present in the body without causing noticeable symptoms. Hepatitis B is one example. In some people, treatment with a biologic can allow a previous hepatitis B infection to become active again. Your clinician may therefore review your hepatitis B history and arrange blood tests before choosing treatment. Depending on your medical history, exposure risks and local guidance, screening for other infections may also be appropriate.
Do IL-17 inhibitors have infection risks too?
Yes. IL-17 inhibitors also affect immune defenses and can increase the risk of infection. For example, the MedlinePlus drug information for secukinumab warns about bacterial, viral and fungal infections, as well as the risk of TB. A medicine from a different biologic class is not automatically free of infection risk. Your healthcare professional considers the medicine's safety information, your infection history and any other conditions when selecting treatment.
What screening is needed before starting biologics?
Before prescribing a biologic, a rheumatology team usually reviews your medical history, current symptoms, previous infections, vaccination history and other medicines. Screening helps identify infections that may need treatment or closer monitoring before immune-modifying therapy begins.
The European Alliance of Associations for Rheumatology (EULAR) recommendations on infection screening and prevention recommend screening for latent TB before starting biologic disease-modifying antirheumatic drugs. Depending on the medicine and your circumstances, assessment may include:
- TB testing: A blood test or skin test may be used to look for latent infection. A blood test called an interferon-gamma release assay is preferred by EULAR where available.
- Hepatitis B assessment: Blood tests and your medical history help the clinician identify infection or a risk of reactivation and determine whether preventive treatment or monitoring is needed.
- Review of other infection risks: Your clinician may consider other tests, such as those for hepatitis C or HIV, based on relevant guidelines and individual risk factors.
- Review of current illness: A suspected or confirmed active infection may need assessment and treatment before a biologic is started.
If screening finds a latent infection, it does not necessarily mean you can never receive a biologic. The healthcare team will assess the results and decide whether treatment, preventive medication, further testing or a change in the treatment plan is needed. Tell the team about previous test results or treatments, even if you no longer have symptoms.
How can you reduce infection risk while taking a biologic?
Keep vaccinations up to date
Vaccination can help protect against infections that may be more concerning when immune defenses are reduced. Before starting treatment, ask which vaccines are appropriate for your age, medical history and location. These may include influenza, pneumococcal, COVID-19 and shingles vaccines, according to local recommendations. Whenever possible, the vaccination schedule should be reviewed before treatment begins because timing can affect how well some vaccines work.
The U.S. Centers for Disease Control and Prevention guidance on altered immune function explains that non-live vaccines can generally be given safely to people with weakened immune defenses, although their effectiveness may vary. Live vaccines may pose a safety concern during immune-suppressing treatment and are generally avoided or need to be considered before therapy. Do not receive a live vaccine or change your biologic schedule without advice from your healthcare team.
Use everyday infection-prevention measures
Simple habits can help lower exposure to germs. Wash your hands regularly, clean and cover cuts, follow food-safety advice, and avoid close contact with people who have a contagious illness when practical. Let your healthcare team know if you have been exposed to an infection that may be particularly important for someone whose immune system is affected, such as chickenpox or shingles when you are not known to be immune.
Tell your clinician about every medicine you take
Make sure your rheumatologist knows about prescription medicines, over-the-counter products and any additional treatment prescribed by another clinician. Other medicines that suppress immune function can affect the overall risk of infection. Do not start, stop or reduce a prescribed medicine on your own to try to prevent infection. Your treatment team can review whether any changes are appropriate.
What symptoms should you report during treatment?
Contact your healthcare team promptly if you develop symptoms that may suggest an infection, especially if they are persistent, worsening or unusual for you. Warning signs can include:
- Fever, chills or sweating that has no clear explanation.
- A new or worsening cough, shortness of breath or coughing up blood.
- Unexplained weight loss, night sweats or unusual, persistent tiredness.
- Skin that becomes red, warm, swollen or painful, or a wound that appears infected.
- Burning, pain or frequent urges when passing urine.
- Persistent diarrhea, stomach pain or other symptoms that may indicate an infection.
These symptoms can have several causes, but infection needs to be considered in someone receiving biologic treatment. A serious infection does not always begin with a high fever. Seek urgent medical assessment if you become rapidly unwell, have difficulty breathing or experience other severe symptoms. If TB symptoms develop, inform your healthcare team promptly even if you had a negative screening test before starting treatment.
Should you delay a biologic dose if you develop an infection?
The right response depends on the infection, its severity and the medicine you take. Some infections may require a temporary delay in treatment, while others may not require the same approach. Contact your prescribing team as soon as possible if you think you have an infection, and ask what to do before your next scheduled dose. If you need antibiotics or assessment from another clinician, tell them that you are taking a biologic.
Do not permanently stop your medicine or change the dosing schedule without medical guidance. Your clinician can determine whether treatment should be paused, when it is appropriate to restart, and whether additional tests or treatment are needed. This helps balance the need to manage infection against the risk of ankylosing spondylitis symptoms returning when treatment is interrupted.
Is the benefit of biologic treatment worth the infection risk?
For many people with active ankylosing spondylitis, biologics can reduce inflammation and improve symptoms when other treatments have not provided enough relief. The decision to use one is based on the expected benefit as well as possible harms. Infection risk is one important part of that decision, alongside your medical history, other conditions, treatment preferences and the effects of the disease on daily life.
Screening, vaccination planning, awareness of warning signs and communication with your rheumatology team can help make treatment safer. Having an infection risk does not automatically mean a biologic is unsuitable. The aim is to choose a treatment that controls inflammation while identifying and managing infection risks as early as possible.