# Positive Human Immunodeficiency Virus (HIV) Test Following Influenza Vaccination: A Case Report

## TL;DR

An elderly woman on dialysis had a false-positive HIV test after a flu shot, highlighting the need for caution in interpreting HIV results in recently vaccinated individuals.

## Contribution

This case report documents a rare false-positive HIV ELISA result following influenza vaccination in an elderly hemodialysis patient.

## Key findings

- An 82-year-old hemodialysis patient had a false-positive HIV ELISA test after influenza vaccination.
- Subsequent testing confirmed the result reverted to negative, confirming the initial result was false.
- The case underscores the importance of considering cross-reactivity in HIV testing among recently vaccinated individuals.

## Abstract

False-positive human immunodeficiency virus (HIV) test results following influenza vaccination are rare today. However, with evolving vaccine formulations, unexpected cross-reactivity remains a potential concern. This case highlights the importance of recognizing this phenomenon to prevent misdiagnosis and patient anxiety.

After obtaining her annual flu shot, an 82-year-old woman on hemodialysis (HD) was repeatedly discovered to have positive HIV enzyme-linked immunosorbent assay (ELISA) test results without having risk factors, and previously, the test was negative. As described in the literature, subsequent testing during the anticipated reversion period demonstrated a return to negativity, confirming a false-positive result.

Cross-reactivity between HIV ELISA tests and influenza vaccines has been reported infrequently due to potential immunologic interactions. This case shows the necessity of interpreting positive HIV results with caution, especially in recently vaccinated individuals and populations undergoing frequent serological testing, such as HD patients.

Clinicians should be aware of the cross-reactivity between the HIV ELISA test and the flu vaccination to recognize false-positive results, even with current influenza vaccine formulations. Awareness of this can prevent unnecessary patient distress, misdiagnosis, and unwarranted interventions.