Surreal image of a blood transfusion bag symbolizing transient immunity.

Hidden Threats: Understanding Transient Hepatitis B Immunity from Blood Transfusions

Reese Marlowe in Health & Wellness November 2025 • 4 min read.

"A closer look at how passively acquired antibodies can temporarily mask a patient's true immunity status."

Blood transfusions, while life-saving, can sometimes carry unexpected baggage. Recipients of blood products—whether whole blood, plasma, or platelets—are known to passively acquire antibodies from donors. This means that the recipient's blood tests may temporarily show immunity to certain diseases, even if they weren't immune before.

While this phenomenon is generally understood, it's not always clearly documented, especially after transfusions of packed red blood cells (PRBC). PRBC contain only a small amount of donor plasma, making the passive transfer of antibodies seem less likely to cause significant effects. However, a recent case highlights how even PRBC transfusions can lead to a temporary state of immunity, with important implications for patient care.

This article delves into a fascinating case where a patient appeared to develop immunity to hepatitis B following a PRBC transfusion. We'll explore the details of the case, the challenges it presented, and what it means for how medical professionals interpret blood test results in transfused patients.

The Case: A Transient Immunity Mystery

Surreal image of a blood transfusion bag symbolizing transient immunity.

A 38-year-old man was admitted to the hospital for investigation of fatigue, weight loss, and anemia. Initially, his hepatitis serology tests came back negative for hepatitis A, B, and C, indicating a non-immune and non-infected status. However, after receiving a third unit of PRBC, a repeat test showed a surprising result: the patient now appeared to have immunity to hepatitis B, with detectable hepatitis B surface antibodies (HBsAb).

This unexpected finding raised several questions. Had the patient somehow contracted and cleared the infection in a matter of hours? Was there a lab error? Further investigation revealed the answer. The third PRBC unit, it turned out, contained a very high concentration of HBsAb from the donor. This passive transfer of antibodies was responsible for the temporary appearance of immunity in the recipient.

False Positives: Understand how passive transfer can lead to misleading test results.
Limited Plasma: Recognize that even PRBC transfusions, despite minimal plasma, can transfer antibodies.
Clinical Impact: Be aware of the potential implications for diagnosis and treatment decisions.
Follow-Up: Implement strategies for monitoring and confirming true immunity status in transfused patients.

The investigation didn't stop there. Segments from the PRBC units transfused after the initial negative HBsAb results were retrieved and tested. The third unit showed a significant concentration of HBsAb, while the fourth unit did not. This confirmed that the passive transfer of antibodies from the third unit was indeed the cause of the transient immunity. Interestingly, the patient's HBsAb levels declined rapidly, with a calculated half-life of only 1.4 days. Follow-up bloodwork two months after discharge confirmed a return to a non-immune status.

Implications for Patient Care

This case underscores the importance of careful interpretation of viral serology test results in patients who have received blood transfusions. A positive antibody result doesn't always indicate true immunity. Passively acquired antibodies can temporarily mask a patient's true immune status, potentially leading to incorrect diagnoses and inappropriate treatment decisions. Medical professionals should be aware of this phenomenon and consider the possibility of passive antibody transfer when interpreting test results in transfused patients. Ideally, baseline viral serology should be drawn prior to transfusion of any blood components or IVIg. False-positive results of viral serology remain a possibility for up to five half-lives of IgG, which may extend to up to 5 months post-transfusion.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1111/tme.12560, Alternate LINK

Title: Transient Hepatitis B Immunity Passively Acquired From Transfusion Of Packed Red Blood Cells

Subject: Hematology

Journal: Transfusion Medicine

Publisher: Wiley

Authors: O. Prokopchuk‐Gauk, A. S. Khan, S. Misskey, M. E. Lyon, A. W. Lyon

Published: 2018-10-12

Everything You Need To Know

How can blood transfusions lead to a temporary false positive for hepatitis B immunity?

Blood transfusions, particularly those involving packed red blood cells (PRBC), can sometimes introduce antibodies from the donor into the recipient's system. This is known as passive antibody transfer. If the donor has hepatitis B surface antibodies (HBsAb), the recipient may temporarily test positive for hepatitis B immunity, even if they were not immune before. This can create a false impression of immunity.

Can packed red blood cell transfusions cause transient hepatitis B immunity, even with minimal plasma?

Even though packed red blood cells (PRBC) contain a limited amount of plasma compared to whole blood or plasma transfusions, they can still carry a sufficient concentration of hepatitis B surface antibodies (HBsAb) to cause transient immunity. The concentration of antibodies in the PRBC unit and the recipient's baseline immunity status determine the impact. This is especially true if the donor has high antibody titers.

What precautions should medical professionals take when interpreting hepatitis B test results in patients who have received blood transfusions?

Medical professionals need to be aware that a positive hepatitis B surface antibody (HBsAb) test result in a recently transfused patient may not always indicate true immunity. It's crucial to consider the patient's transfusion history and interpret test results cautiously. Baseline viral serology should be drawn prior to transfusion of any blood components. False-positive results of viral serology remain a possibility for up to five half-lives of IgG, which may extend to up to 5 months post-transfusion. Additional testing or monitoring may be necessary to confirm true immunity status, especially when making decisions about vaccination or antiviral treatment.

Can you provide an example of transient hepatitis B immunity following a packed red blood cell transfusion?

In a 38-year-old man who received a packed red blood cell (PRBC) transfusion, subsequent testing revealed the presence of hepatitis B surface antibodies (HBsAb), suggesting immunity to hepatitis B. However, further investigation revealed that this apparent immunity was due to passive transfer of antibodies from the donor's blood, as the third PRBC unit had a high concentration of HBsAb. Follow-up bloodwork confirmed that the patient's HBsAb levels declined rapidly, and he returned to a non-immune status, demonstrating the transient nature of passively acquired immunity.

What steps can be taken to accurately assess hepatitis B immunity status following a blood transfusion to avoid false conclusions?

To accurately determine a patient's hepatitis B immunity status after a blood transfusion, it is recommended to conduct baseline viral serology prior to transfusion. When interpreting viral serology test results, consider the possibility of passive antibody transfer, especially within the first few months after transfusion. Monitor HBsAb levels over time to distinguish between true immunity and transient passive transfer. If necessary, delay decisions about vaccination or antiviral treatment until the passively acquired antibodies have cleared and the patient's true immune status can be determined.