Magnus, Per, Gunnes, Nina, Tveito, Kari et al. · Vaccine · 2015 · DOI
This large study of the Norwegian population during the 2009 flu pandemic found that people who caught the H1N1 influenza virus were more than twice as likely to develop ME/CFS afterward. However, people who received the pandemic flu vaccine did not show an increased risk of developing ME/CFS. This suggests that actually getting infected with the flu virus itself, rather than the vaccine, may trigger ME/CFS in some people.
This study directly addresses a major concern among ME/CFS patients by examining whether the pandemic flu vaccine triggers CFS/ME. Using comprehensive national health data, it provides reassurance that the vaccine was not associated with increased CFS/ME risk while strengthening evidence that infectious triggers—specifically symptomatic influenza infection—may be involved in disease pathogenesis.
This study does not establish the mechanism by which influenza infection triggers CFS/ME, nor does it explain why only some infected individuals develop the condition. It cannot determine causation definitively—only association—and uses specialist health care diagnoses, which may underestimate true CFS/ME prevalence if many cases remain undiagnosed. The findings are specific to pandemic H1N1 and may not generalize to other influenza strains or non-influenza infections.
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
Magnus, Per, Gunnes, Nina, Tveito, Kari, Bakken, Inger Johanne, Ghaderi, Sara, Stoltenberg, Camilla, et al. (2015). Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) is associated with pandemic influenza infection, but not with an adjuvanted pandemic influenza vaccine.. Vaccine. https://doi.org/10.1016/j.vaccine.2015.10.018
BibTeX
@article{mecfsatlas-magnus-2015-chronic-fatigue,
author = {Magnus, Per and Gunnes, Nina and Tveito, Kari and Bakken, Inger Johanne and Ghaderi, Sara and Stoltenberg, Camilla and Hornig, Mady and Lipkin, W Ian and Trogstad, Lill and Håberg, Siri E},
title = {Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) is associated with pandemic influenza infection, but not with an adjuvanted pandemic influenza vaccine.},
journal = {Vaccine},
year = {2015},
doi = {10.1016/j.vaccine.2015.10.018},
note = {PubMed: 26475444},
url = {https://www.mecfsatlas.com/evidence/magnus-2015-chronic-fatigue},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-26. https://www.mecfsatlas.com/evidence/magnus-2015-chronic-fatigue
Contribute
Private, reviewed by a human. Not a public comment thread.