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Does Fasenra weaken your immune system?

Medically reviewed by Carmen Pope, BPharm. Last updated on March 28, 2023.

Does Fasenra lower your immune system?

Official answer


Fasenra (benralizumab) is a monoclonal antibody that is used to treat eosinophilic asthma and it does this by affecting the way your immune system works, which raises legitimate concerns that it could cause immunosuppression and negatively impact a person's immune response.

Fasenra works by depleting eosinophils, which are a type of white blood cells and part of the immune system that helps fight infection and cancer. Because of this, researchers are conducting ongoing investigations to determine whether Fasenra weakens the immune system and puts patients at increased risk of infection and cancer. No major safety concerns, however, have been identified to date.

Fasenra does not appear to weaken the immune system

Current research suggests that Fasenra:

  • Does not increase the risk of infection
  • Does not increase the risk of cancer
  • Does not stop patients from responding to seasonal influenza vaccination
  • Does not lower total antibody (immunoglobulin) concentrations in the blood, which help fight foreign invaders (antigens).

Fasenra is a monoclonal antibody (IgG1, kappa) that binds to the alpha subunit of the interleukin-5 (IL-5) receptor. It activates the immune system to lower the number of eosinophils in the blood in patients with eosinophilic asthma, which is associated with increased numbers of these white blood cells. Fasenra works by blocking IL-5, enhancing the ability of natural killer cells and by depleting basophils.

  • Jackson DJ, Korn S, Mathur SK, et al. Safety of Eosinophil-Depleting Therapy for Severe, Eosinophilic Asthma: Focus on Benralizumab. Drug Saf 43, 409–425 (2020).
  • European Medicines Agency (EMA). Fasenra (benralizumab). An overview of Fasenra and why it is authorised in the EU. [Accessed May 25, 2020]. Available online at:
  • Zeitlin PL, Leong M, Cole J, et al. Benralizumab Does Not Impair Antibody Response to Seasonal Influenza Vaccination in Adolescent and Young Adult Patients With Moderate to Severe Asthma: Results From the Phase IIIb ALIZE Trial. J Asthma Allergy. 2018 Nov 20;11:181-192. doi: 10.2147/JAA.S172338.

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