Seidel, Maximilian, Anft, Moritz, Wiemers, Lea et al. · Immunology letters · 2026 · DOI
Researchers gave a monoclonal antibody treatment (Tixagevimab/Cilgavimab) to nine immunodeficient patients with long COVID and ME/CFS-like symptoms who had detectable coronavirus spike protein in their blood. After 30 days, one immune marker (β1-adrenergic receptor autoantibody) showed a modest decrease, but spike protein levels and symptom outcomes did not change significantly as a group. These are very preliminary findings from a small study without a control group, and the authors emphasise that efficacy remains uncertain.
This study addresses a hypothesis relevant to ME/CFS research—that persistent circulating spike protein may contribute to post-COVID illness—and reports preliminary immunological changes in one biomarker in a subset of immunodeficient patients. However, the findings remain exploratory and hypothesis-generating; they do not establish that spike protein reduction treats ME/CFS or long COVID, nor do they confirm the mechanism. Clinicians and patients should view these results as a small, early signal requiring larger, controlled studies before clinical application is considered.
This study does not establish that Tixagevimab/Cilgavimab treats or improves ME/CFS or long COVID. It does not confirm that persistent spike protein causes ME/CFS-like symptoms, nor does it demonstrate that reducing spike protein or autoantibody levels leads to clinical benefit. The findings do not generalise beyond the nine immunodeficient patients studied, do not control for placebo or natural recovery, and do not account for confounders in an uncontrolled setting.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Seidel, Maximilian, Anft, Moritz, Wiemers, Lea, Seibert, Felix S, Bertram, Sebastian, Rosiewicz, Kamil, et al. (2026). Exploratory clinical and immunological changes following Tixagevimab/Cilgavimab administration in immunodeficient patients with SARS-CoV-2-associated ME/CFS and persistent circulating spike protein.. Immunology letters. https://doi.org/10.1016/j.imlet.2026.107247
BibTeX
@article{mecfsatlas-seidel-2026-exploratory-clinical,
author = {Seidel, Maximilian and Anft, Moritz and Wiemers, Lea and Seibert, Felix S and Bertram, Sebastian and Rosiewicz, Kamil and Stervbo, Ulrik and Westhoff, Timm H and Babel, Nina},
title = {Exploratory clinical and immunological changes following Tixagevimab/Cilgavimab administration in immunodeficient patients with SARS-CoV-2-associated ME/CFS and persistent circulating spike protein.},
journal = {Immunology letters},
year = {2026},
doi = {10.1016/j.imlet.2026.107247},
note = {PubMed: 42843426},
url = {https://www.mecfsatlas.com/evidence/seidel-2026-exploratory-clinical},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-10-09. https://www.mecfsatlas.com/evidence/seidel-2026-exploratory-clinical
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