Krogsgaard, Lene Wulff, Petersen, Irene, Plana-Ripoll, Oleguer et al. · PLoS medicine · 2021 · DOI
This study examined whether having an infection around the time of HPV vaccination increases the risk of developing illness symptoms afterward in Danish women. Researchers found that women who had a treated infection within one month before or after their first HPV vaccine dose were more likely to later seek care at specialized centers for suspected vaccine side effects. The symptoms reported were similar to those seen in chronic fatigue syndrome.
This is the first study to systematically investigate whether infection timing relative to HPV vaccination triggers CFS-like symptoms in a subset of vaccine recipients. Understanding this potential mechanism is crucial for ME/CFS research, as infection is a well-established trigger for post-infectious CFS, and clarifying vaccine-infection interactions may help identify vulnerable subgroups and prevent illness onset.
This study does not prove that HPV vaccination causes CFS or that infection during vaccination directly causes adverse effects—it shows an association only. The study cannot establish causation, and heightened symptom reporting or healthcare-seeking behavior among those with recent infections may partially explain the findings. Additionally, the study endpoint was specialist referral for suspected effects, not confirmed diagnoses of CFS or verified adverse outcomes.
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
Krogsgaard, Lene Wulff, Petersen, Irene, Plana-Ripoll, Oleguer, Bech, Bodil Hammer, Lützen, Tina Hovgaard, Thomsen, Reimar Wernich, et al. (2021). Infections in temporal proximity to HPV vaccination and adverse effects following vaccination in Denmark: A nationwide register-based cohort study and case-crossover analysis.. PLoS medicine. https://doi.org/10.1371/journal.pmed.1003768
BibTeX
@article{mecfsatlas-krogsgaard-2021-infections-temporal,
author = {Krogsgaard, Lene Wulff and Petersen, Irene and Plana-Ripoll, Oleguer and Bech, Bodil Hammer and Lützen, Tina Hovgaard and Thomsen, Reimar Wernich and Rytter, Dorte},
title = {Infections in temporal proximity to HPV vaccination and adverse effects following vaccination in Denmark: A nationwide register-based cohort study and case-crossover analysis.},
journal = {PLoS medicine},
year = {2021},
doi = {10.1371/journal.pmed.1003768},
note = {PubMed: 34495975},
url = {https://www.mecfsatlas.com/evidence/krogsgaard-2021-infections-temporal},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-25. https://www.mecfsatlas.com/evidence/krogsgaard-2021-infections-temporal
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