Smallpox Monkeypox Vaccine and Belumosudil: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 15, 2026 · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Belumosudil
Smallpox Monkeypox Vaccine
No brand names on record
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
Belumosudil (Rezurock) is a medicine that calms down an overactive immune system, which is why it helps with graft-versus-host disease. The smallpox/monkeypox vaccine is a live vaccine, meaning it uses a weakened form of the virus to teach your body to fight it.
Here is the concern: because belumosudil quiets your immune defenses, your body may not be able to keep even the weakened vaccine virus in check. That could let the vaccine actually cause an infection instead of just protecting you. This is why the two should generally not be combined. The good news is your care team can plan your vaccine timing safely, so please talk with your doctor or pharmacist before getting any live vaccine.
Interaction: Belumosudil is an immunosuppressant (ROCK2 inhibitor) used in chronic GVHD. Live replicating vaccines such as the smallpox/monkeypox (vaccinia-based) vaccine are contraindicated in immunosuppressed patients.
- Mechanism: Drug-induced attenuation of immune response permits uncontrolled replication of the live vaccine strain, risking disseminated vaccine-derived infection.
- Direction: Increased risk of vaccine-induced infection (neither agent is a prodrug; this is a PD immunosuppression effect).
- Evidence: Established. Severity: Contraindicated.
Management: Avoid live vaccination during immunosuppression. Consider only after documented immune reconstitution and off immunosuppressive therapy per guideline intervals.
What happens
An increased risk of infection by the live vaccine
Interaction Deep Dive
The smallpox and monkeypox vaccine should not be given to people who have severe immunodeficiency 2. A live vaccine may be given to patients with leukemia, lymphoma, or other malignancies provided their disease is in remission, their immunocompetence has been restored, and at least 3 months have passed since their chemotherapy was stopped 1.
Why it happens (mechanism)
Decreased immune response allows live vaccine to produce infection
How to manage this interaction
Keep taking your belumosudil as prescribed and do not stop it on your own. The key step here is about vaccine timing, not your treatment.
- Live vaccines like the smallpox/monkeypox vaccine are generally not given while your immune system is suppressed.
- Tell any provider offering you a vaccine that you take belumosudil.
- Your care team may wait until your immune function has recovered and immunosuppressive therapy has been stopped for an appropriate period before considering a live vaccine.
- Ask your pharmacist or doctor about safer, non-live vaccine options if you need protection.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Smallpox Monkeypox Vaccine and Belumosudil together?
Do not get the live smallpox/monkeypox vaccine while taking belumosudil, because the weakened immune response can let the vaccine cause an actual infection. Talk with your doctor or pharmacist to plan safe vaccine timing. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Smallpox Monkeypox Vaccine and Belumosudil interaction?
It is rated contraindicated. These should generally not be used together.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How is the Smallpox Monkeypox Vaccine and Belumosudil interaction managed?
Keep taking your belumosudil as prescribed and do not stop it on your own. The key step here is about vaccine timing, not your treatment. Live vaccines like the smallpox/monkeypox vaccine are generally not given while your immune system is suppressed. Tell any provider offering you a vaccine that you take belumosudil. Your care team may wait until your immune function has recovered and immunosuppr… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "established". Well documented — supported by controlled studies or strong clinical data.
Questions for your pharmacist
- Does my dose of Smallpox Monkeypox Vaccine or Belumosudil need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (2)
- Centers for Disease Control and Prevention (CDC): Vaccines & Immunizations: altered immunocompetence. Centers for Disease Control and Prevention (CDC). Atlanta, GA. 2024.
- Product Information: ACAM2000 percutaneous injection, smallpox and mpox (vaccinia) vaccine, live percutaneous injection. Emergent Product Development Gaithersburg Inc (per FDA), Gaithersburg, MD, 2024. DailyMed
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