PACVS vs MCAS: symptoms, biomarkers, trials and researchliterature-only comparison
A data-driven comparison of Post-Acute COVID-19 Vaccination Syndrome (PACVS) and Mast Cell Activation Syndrome (MCAS) built from the Open Source Medicine Foundation biomarker atlases, PubMed literature feeds, ClinicalTrials.gov registry extract and post-acute infection syndrome (PAIS) cohort database.
Mast-cell activation is one of several proposed mechanisms for post-vaccination syndrome, and antihistamine protocols are used empirically. Both conditions lack a consensus case definition.
No biomarker atlas exists for MCAS, so the biomarker sections below are limited to the other condition. This page compares literature, trials, therapeutics and cohorts.
What each condition is
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
Mast Cell Activation Syndrome
Also known as: Mast cell activation disorder
MCAS is characterised by episodic, multi-system symptoms (flushing, hives, gastrointestinal upset, wheeze, hypotension) caused by inappropriate release of mast-cell mediators, with laboratory evidence such as a rise in serum tryptase during an episode and a response to mast-cell-directed therapy. Diagnostic criteria remain contested between consensus groups. MCAS is frequently reported alongside POTS, hypermobility and post-infectious illness; OSMF follows it through a literature feed and clinical-trial registry rather than a dedicated biomarker atlas.
OSMF resources: literature feed
Side-by-side summary
| Measure | PACVS | MCAS |
|---|---|---|
| Biomarkers catalogued | 32 | No atlas |
| Biomarker categories covered | autoimmune (8), functional (8), spike (4), molecular (4), metabolic (3), serologic (2), inflammatory (2), proteomic (1) | — |
| Markers with LOINC codes | 3 | — |
| Literature studies tracked | 15 | 75 |
| Most recent tracked study | 24 Sep 2026 | 10 Jul 2026 |
| Registered trials (all statuses) | 2 | 5 |
| Recruiting / not yet recruiting | 2 | 1 |
| Active, not recruiting | 0 | 0 |
| Completed | 0 | 1 |
| Terminated / withdrawn / suspended | 0 | 2 |
| Unknown status | 0 | 1 |
| Named cohorts in PAIS database | 4 | 0 |
| Therapeutic agents tracked | 7 | 11 |
Trial condition matching: PACVS uses keyword matching on registry condition and title fields; MCAS uses keyword matching on registry condition and title fields. Trials listing both conditions: 0.
Biomarkers catalogued for PACVS
MCAS has no OSMF biomarker atlas, so no shared-marker matching is possible. The PACVS atlas lists 32 markers; the 15 most relevant to this comparison are shown (autonomic, immune, inflammatory and vascular categories first).
- IL-6 Increased inflammatory
- IL-8 Increased inflammatory
- Heart rate variability (HRV) Decreased functional
- Salivary nitric oxide Decreased functional
- Orthostatic heart rate increment Increased functional
- 6-minute walk distance Decreased functional
- Exertional SpO₂ nadir Decreased functional
- Chester Step Test (VO₂ proxy) Decreased functional
- PAC-19QoL score Decreased functional
- Neurofilament light chain (NfL) Increased functional
- 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
Overlapping therapeutics under investigation (0)
No therapeutic agent is currently tracked for both conditions. PACVS has 7 tracked agents and MCAS has 11; see the therapeutic agents index.
Research cohorts
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
MCAS cohorts (0)
No named cohort for this condition in the PAIS database yet.
Recent research
Latest PACVS studies
Latest MCAS studies
Frequently asked questions
Can you have both PACVS and MCAS?
Yes. MCAS is a syndrome diagnosed on clinical criteria and can be diagnosed in someone who also has PACVS; 0 registered trials in the OSMF registry list both conditions, and no therapeutic agent is currently tracked for both.
How do the biomarker profiles differ?
OSMF does not maintain a biomarker atlas for MCAS, which is diagnosed by physiological or clinical criteria rather than a laboratory panel, so this is a literature-level comparison. PACVS has 32 catalogued markers across 8 categories (most often autoimmune, functional, spike).
Which has more active clinical trials?
PACVS has more: 2 active or recruiting trials versus 1 for MCAS (registry snapshot 07 Oct 2026). Totals including completed, terminated and unknown-status studies are 2 for PACVS and 5 for MCAS. Condition matching for PACVS, MCAS 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 15 recent PubMed-indexed studies for PACVS (latest 24 Sep 2026) and 75 for MCAS (latest 10 Jul 2026). The feeds hold a rolling window of recent publications, so they indicate current publication pace rather than lifetime output. See the PACVS feed and the MCAS feed for the full lists.
Are the same treatments being studied for both?
No therapeutic agent is currently tracked for both PACVS and MCAS in the OSMF trial registry or agent database. That reflects the small or non-overlapping evidence base rather than proof that treatments differ.
Which has larger research cohorts?
The PAIS cohort database lists 4 named cohorts for PACVS and 0 named cohorts for MCAS, the largest being 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_pacvs_vs_mcas,
author = {Open Source Medicine Foundation},
title = {PACVS vs MCAS: symptoms, biomarkers, trials and research compared},
year = {2026},
howpublished = {\url{https://research.opensourcemed.info/compare/pacvs-vs-mcas.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 07 Oct 2026 / 10 Jul 2026; trial registry 07 Oct 2026; atlases 30 Jun 2026 / n/a. Generated by scripts/build_compare_pages.py.