ME/CFS vs PACVS: symptoms, biomarkers, trials and research
A data-driven comparison of Myalgic Encephalomyelitis / Chronic Fatigue Syndrome (ME/CFS) and Post-Acute COVID-19 Vaccination Syndrome (PACVS) built from the Open Source Medicine Foundation biomarker atlases, PubMed literature feeds, ClinicalTrials.gov registry extract and post-acute infection syndrome (PAIS) cohort database.
PACVS cohorts report high rates of post-exertional malaise and fatigue, and some registries explicitly apply ME/CFS criteria. The comparison asks whether a vaccine-triggered syndrome follows the same immunometabolic track as classical ME/CFS.
What each condition is
Myalgic Encephalomyelitis / Chronic Fatigue Syndrome
Also known as: CFS, ME, Systemic Exertion Intolerance Disease
ME/CFS is a chronic, multi-system illness defined clinically by a substantial reduction in activity, post-exertional malaise (PEM), unrefreshing sleep and either cognitive impairment or orthostatic intolerance. It frequently begins after an infection, including mononucleosis (EBV), SARS, Q fever, Ross River virus and now SARS-CoV-2, but many cases have no identified trigger. There is no validated diagnostic test; research biomarkers centre on energy metabolism, immune signalling and autonomic function.
Atlas scope: Molecular, metabolic, immunological, and autonomic alterations in myalgic encephalomyelitis / chronic fatigue syndrome (ME/CFS) compared to healthy sedentary and active controls — including post-exertional malaise (PEM) phenotypes.
OSMF resources: biomarker atlas · literature feed
Post-Acute COVID-19 Vaccination Syndrome
Also known as: PCVS, Post-Vac Syndrome, Post-vaccination syndrome
PACVS (also written PCVS or post-vac syndrome) refers to persistent, Long COVID-like symptoms that begin shortly after SARS-CoV-2 vaccination and last for months in a small subset of recipients. It is not a recognised diagnostic entity in most countries and is defined differently across the handful of registry and survey cohorts that exist (Marburg, Yale LISTEN, VITAE). Research is early-stage: the literature is small, the biomarker evidence comes mainly from case series, and only a few interventional studies are registered.
Atlas scope: Molecular, serologic, immunologic, and functional alterations reported in Post-Acute COVID-19 Vaccination Syndrome (PACVS) — persistent symptoms following SARS-CoV-2 vaccination — from PACVS/PCVS primary studies and post-vaccination adverse-event literature.
OSMF resources: biomarker atlas · literature feed
Side-by-side summary
| Measure | ME/CFS | PACVS |
|---|---|---|
| Biomarkers catalogued | 46 | 32 |
| Biomarker categories covered | inflammatory (10), metabolic (10), autonomic (6), immune (5), mitochondrial (4), functional (4), autoimmune (3), neurological (2), urinary (2) | autoimmune (8), functional (8), spike (4), molecular (4), metabolic (3), serologic (2), inflammatory (2), proteomic (1) |
| Markers with LOINC codes | 13 | 3 |
| Literature studies tracked | 75 | 15 |
| Most recent tracked study | 06 Jul 2026 | 24 Sep 2026 |
| Registered trials (all statuses) | 146 | 2 |
| Recruiting / not yet recruiting | 26 | 2 |
| Active, not recruiting | 9 | 0 |
| Completed | 75 | 0 |
| Terminated / withdrawn / suspended | 15 | 0 |
| Unknown status | 21 | 0 |
| Named cohorts in PAIS database | 3 | 4 |
| Therapeutic agents tracked | 179 | 7 |
Trial condition matching: ME/CFS uses the registry’s mapped condition label; PACVS uses keyword matching on registry condition and title fields. Trials listing both conditions: 0.
Shared biomarkers (6)
Markers catalogued in both atlases, matched by normalised name or LOINC code. Rows marked direction differs are reported to change in opposite or inconsistent directions across the two literatures, which may reflect different comparison groups, assays or disease stages rather than true biology.
| Biomarker | Category | Direction in ME/CFS | Direction in PACVS | Matched by | Sources |
|---|---|---|---|---|---|
| Interleukin-6 (IL-6) IL-6 in PACVS direction differs | inflammatory | Mixed / conflicting vs HC | Increased vs HC | LOINC 26881-5 | Corbitt et al. 2019; Mundorf et al. 2024 |
| Heart rate variability (RMSSD) Heart rate variability (HRV) in PACVS | autonomic / functional | Decreased vs HC | Decreased vs HC | name | Nelson et al. 2019; Mundorf et al. 2024 |
| Orthostatic heart rate increment | autonomic / functional | Increased vs HC | Increased vs HC | name | Nelson et al. 2019; Mundorf et al. 2024 |
| Neurofilament light chain (NfL) direction differs | neurological / functional | Mixed / conflicting vs HC | Increased vs HC | LOINC 94635-5 | Maksoud et al. 2023; Mundorf et al. 2024 |
| 6-minute walk distance | functional | Decreased vs HC | Decreased vs HC | name | Maksoud et al. 2023; Halma 2024 |
| Anti-GPCR autoantibodies (panel) | autoimmune | Increased vs HC — LC/PACVS overlap | Increased vs HC | name | Maksoud et al. 2023; Mantovani et al. 2024 |
Distinct biomarkers
Top 15 markers catalogued for one condition but not matched in the other. Full lists are on the ME/CFS atlas and the PACVS atlas.
Only in ME/CFS atlas (40)
- Interleukin-1 (IL-1α/β) Increased inflammatory
- Transforming Growth Factor-β (TGF-β) Increased inflammatory
- Tumor Necrosis Factor-α (TNF-α) Mixed / conflicting inflammatory
- Interleukin-8 (IL-8 / CXCL8) Mixed / conflicting inflammatory
- Interleukin-10 (IL-10) Mixed / conflicting inflammatory
- C-Reactive Protein (CRP) Mixed / conflicting inflammatory
- Leptin Increased inflammatory
- Resistin Mixed / conflicting inflammatory
- Acylcarnitines (composite) Increased metabolic
- C16 Acylcarnitine (palmitoylcarnitine) Increased metabolic
- C18 Acylcarnitine (stearoylcarnitine) Increased metabolic
- Free carnitine Mixed / conflicting metabolic
- Lactate (blood) Increased metabolic
- ATP production capacity Decreased mitochondrial
- Mitochondrial membrane potential Decreased mitochondrial
+25 more in the atlas.
Only in PACVS atlas (26)
- S1 in CD16+ monocytes Increased spike
- Circulating spike (post-mRNA myocarditis) Increased spike
- Spike in cutaneous lesions Increased spike
- Spike in neurological tissue Increased spike
- Anti-Spike (Anti-S) antibodies Increased serologic
- Anti-Nucleocapsid (Anti-N) antibodies Decreased serologic
- 2P proteotypic peptides (K986P/V987P) Increased molecular
- Wild-type viral spike peptides Decreased molecular
- BNT162b2 vaccine mRNA (qPCR) Mixed / conflicting molecular
- Vaccine mRNA (hybrid 3'UTR motifs) Mixed / conflicting molecular
- Anti-ACE2 autoantibodies Increased autoimmune
- Anti-AT1R (angiotensin II type 1 receptor) Increased autoimmune
- Anti-MAS1 receptor autoantibodies Increased autoimmune
- Anti-STAB1 autoantibodies Increased autoimmune
- Anti-ADRA2A (α2B adrenergic receptor) Decreased autoimmune
+11 more in the atlas.
Overlapping therapeutics under investigation (2)
Agents that appear in registered trials or the OSMF therapeutic-agent database for both ME/CFS and PACVS. Inclusion means an agent is being studied, not that it works.
- Intravenous Immunoglobulin (IVIG)
- N-Acetylcysteine (NAC)
Research cohorts
ME/CFS cohorts (3)
- DecodeME ME/CFS GWAS registry linkage, n=15,579, biobank active
- UK ME/CFS Biobank (CureME, LSHTM) cross sectional, n=632, biobank active
- NIH Intramural ME/CFS Deep-Phenotyping Study (Walitt/Nath 2024) cross sectional, n=57, biobank active
PACVS cohorts (4)
- Post-Vac-Syndrom Deutschland patient survey survey, n=777, biobank not_applicable
- VITAE vaccine-injury survey (Halma & Varon) survey, n=706, biobank not_applicable
- Yale LISTEN post-vaccination syndrome cohort (Krumholz) survey, n=241, biobank active
- PACVS registry cohort (Semmler/Mundorf) cross sectional, n=191, biobank unknown
Recent research
Latest ME/CFS studies
Latest PACVS studies
Frequently asked questions
Can you have both ME/CFS and PACVS?
They are not mutually exclusive. Both are diagnosed clinically, and a person can meet criteria for ME/CFS and PACVS at the same time. In the OSMF data the two conditions share 6 catalogued biomarkers, 0 registered trials list both conditions, and 0 cohorts in the PAIS database are relevant to both. Overlap in a dataset is not evidence that one condition causes the other.
How do the biomarker profiles differ?
ME/CFS has 46 catalogued markers, led by inflammatory (10), metabolic (10), autonomic (6). PACVS has 32, led by autoimmune (8), functional (8), spike (4). 6 markers appear in both atlases, and 2 of those are reported to move in different directions (Interleukin-6 (IL-6), Neurofilament light chain (NfL)). Categories unique to ME/CFS: autonomic, immune, mitochondrial, neurological, urinary; unique to PACVS: molecular, proteomic, serologic, spike.
Which has more active clinical trials?
ME/CFS has more: 35 active or recruiting trials versus 2 for PACVS (registry snapshot 07 Oct 2026). Totals including completed, terminated and unknown-status studies are 146 for ME/CFS and 2 for PACVS. Condition matching for PACVS relies on keyword matching of registry condition fields and may miss trials. Trial counts measure research attention, not treatment efficacy.
Which condition has more recent research?
OSMF tracks 75 recent PubMed-indexed studies for ME/CFS (latest 06 Jul 2026) and 15 for PACVS (latest 24 Sep 2026). The feeds hold a rolling window of recent publications, so they indicate current publication pace rather than lifetime output. See the ME/CFS feed and the PACVS feed for the full lists.
Are the same treatments being studied for both?
2 agents appear in the trial registry or therapeutic-agent database for both conditions, including Intravenous Immunoglobulin (IVIG), N-Acetylcysteine (NAC). All of these are investigational for these indications; none is an approved treatment for either condition. Overlap usually reflects shared hypotheses (immune modulation, autonomic support, antiviral or anti-inflammatory strategies) rather than demonstrated efficacy.
Which has larger research cohorts?
The PAIS cohort database lists 3 named cohorts for ME/CFS and 4 named cohorts for PACVS, the largest being DecodeME ME/CFS GWAS (15,579 enrolled) and Post-Vac-Syndrom Deutschland patient survey (777 enrolled). Cohorts with stored biospecimens and open external access are the most useful for cross-condition biomarker validation.
Related comparisons
Cite this page
@misc{osmf_mecfs_vs_pacvs,
author = {Open Source Medicine Foundation},
title = {ME/CFS vs PACVS: symptoms, biomarkers, trials and research compared},
year = {2026},
howpublished = {\url{https://research.opensourcemed.info/compare/me-cfs-vs-pacvs.html}},
note = {Data as of 2026-10-07}
}Get OSMF research updates
New biomarker, trial and cohort data, summarised for patients and researchers.
Last updated 07 Oct 2026 (page build). Underlying data: literature feeds 06 Jul 2026 / 07 Oct 2026; trial registry 07 Oct 2026; atlases 29 Jun 2026 / 30 Jun 2026. Generated by scripts/build_compare_pages.py.