Post-Acute COVID-19 Vaccination Syndrome (PACVS) describes persistent, multi-system symptoms that begin within days to weeks of COVID-19 vaccination and last for months or years.
Also known as post-vaccination syndrome (PVS), PCVS and Post-Vac-Syndrom.
Severity varies widely
Some people keep up most daily activities. Others become partially or fully disabled.
Often presents as a known syndrome
PACVS can present as recognised diagnoses such as postural orthostatic tachycardia syndrome (POTS), small-fibre neuropathy or ME/CFS.
Symptoms by body system
PACVS is multi-system. These are the symptoms most often described.
Fatigue & energy
- Profound fatigue unrelieved by rest
- Post-exertional malaise (PEM)
- Exercise intolerance
Neurological
- Brain fog
- Memory and concentration problems
- Neuropathic pain
- Small-fibre neuropathy
Cardiovascular
- Palpitations
- Chest pain
- Blood pressure changes
- Shortness of breath
Autonomic
- Orthostatic intolerance / POTS
- Dizziness on standing
- Temperature dysregulation
- Abnormal sweating
Sleep & mood
- Unrefreshing sleep
- Insomnia
- Anxiety
- Low mood
Other
- Gastrointestinal symptoms
- Joint and muscle pain
- Headache
- Skin reactions
Post-exertional malaise (PEM)
A hallmark symptom is post-exertional malaise (PEM), meaning a marked worsening of symptoms after physical or mental exertion. It often appears 24–72 hours after the activity, which makes triggers hard to identify. Pacing, meaning managing activity to stay within your energy limits, is the main way to manage PEM.
PACVS or normal vaccine side effects?
Normal reactions such as a sore arm, mild fever or a few days of fatigue resolve within one to two weeks. PACVS involves persistent, often disabling symptoms that last months or years, and can meet criteria for ME/CFS, POTS or small-fibre neuropathy.
Which symptoms go with which mechanism
Each of the seven proposed mechanism groups is linked to a typical set of symptoms. The last column shows how strong the evidence for that mechanism is in PACVS specifically.
| Mechanism | Typical symptoms | Evidence in PACVS |
|---|---|---|
| Persistent antigen | Fatigue, Relapsing–remitting course, Multi-system symptoms | Emerging |
| Immune dysregulation | Fatigue, Flu-like malaise, Sore throat / tender lymph nodes, Sleep disturbance | Emerging |
| Autoimmunity | Orthostatic intolerance, Palpitations, Neurological symptoms, Fatigue | Emerging |
| Vascular & clotting | Exercise intolerance, Chest discomfort, Brain fog, Cold extremities | Hypothesis |
| Mitochondria & metabolism | Post-exertional malaise, Muscle fatigue and pain, Exercise intolerance, Fatigue | Hypothesis |
| Autonomic & nerve | Tachycardia on standing, Burning or tingling pain, Temperature intolerance, GI dysmotility | Emerging |
| Neuroinflammation | Brain fog, Memory and word-finding problems, Unrefreshing sleep, Headache | Hypothesis |
Lab findings reported in PACVS patients
Published PACVS cohorts and case series have reported the measurable findings below, some of them associated with particular symptoms. These are group-level research findings, not a diagnostic test.
| Finding | Change | Type | What was reported |
|---|---|---|---|
| S1 spike subunit in CD16+ monocytes | ↑ | Spike protein & exposure markers | Detected by flow cytometry in people with post-vaccine syndrome (n=50) vs asymptomatic vaccinated controls (n=26), up to 245 days after vaccination; prior infection excluded by history and anti-nucleocapsid testing.[1] |
| Anti-spike (anti-S) antibodies | + | Spike protein & exposure markers | Positive in a PACVS case series (n=17, never infected); an exposure marker rather than a disease marker, since vaccinated people generally develop them.[2,3] |
| Anti-nucleocapsid (anti-N) antibodies | ↓ | Spike protein & exposure markers | Expected to be negative in vaccine-only PACVS (the vaccines do not contain nucleocapsid); used to rule out prior infection.[1,3] |
| Vaccine-derived spike or mRNA sequences | + | Spike protein & exposure markers | Proposed candidate markers (vaccine-sequence mRNA; mass-spectrometry differentiation of vaccine vs viral spike). LC-MS was used to confirm S1 in one cohort; no validated case-control assay yet.[1,3] |
| Anti-MAS1 receptor autoantibodies | + | GPCR & renin-angiotensin autoantibodies | Positive in 16/17 (94%) PACVS patients; associated with widespread burning sensation. Case series without a control group.[2] |
| Anti-ACE2 autoantibodies | + | GPCR & renin-angiotensin autoantibodies | Positive in 11/17 (65%); associated with ecchymosis, skin oedema and rash; proposed as a candidate PACVS biomarker.[2] |
| Anti-AT1R (angiotensin II type 1 receptor) autoantibodies | ↑ | GPCR & renin-angiotensin autoantibodies | Reported as increased in PACVS vs the normal post-vaccination state (registry, n=191); in a case series associated with lymphadenopathy/tonsillitis.[2,4] |
| Anti-α2B-adrenergic receptor autoantibodies | ↓ | GPCR & renin-angiotensin autoantibodies | Reported as decreased in PACVS vs the normal post-vaccination state.[4] |
| Anti-α2A-adrenergic receptor (ADRA2A) autoantibodies | ↕ | GPCR & renin-angiotensin autoantibodies | Levels inversely associated with memory loss/brain fog in a 17-patient case series.[2] |
| Anti-STAB1 (stabilin-1) autoantibodies | + | GPCR & renin-angiotensin autoantibodies | Associated with skin oedema and rash in a 17-patient case series.[2] |
| Anti-muscarinic M3 (CHRM3) autoantibodies | + | GPCR & renin-angiotensin autoantibodies | Above threshold in 8/17 (47%) PACVS patients, usually together with anti-CHRM4.[2] |
| Anti-GPCR autoantibody panel (16 targets) | + | GPCR & renin-angiotensin autoantibodies | A high share of patients were positive for several GPCR autoantibodies (most often MAS1, ACE2, CHRM4, ADRA1A, ADRB2).[2] |
| Anti-idiotype antibodies (ACE2 vs anti-S) | ↕ | GPCR & renin-angiotensin autoantibodies | ACE2 autoantibody levels correlated with anti-S titres, consistent with a proposed anti-idiotype mechanism; hypothesis-level evidence.[2,5] |
| IL-6 and IL-8 | ↑ | Inflammation & tryptophan-kynurenine pathway | Elevated in >80% of a PACVS registry cohort (n=191).[4] |
| Blood lactate during exercise (lactate threshold) | ↑ | Energy metabolism & fatty-acid oxidation | Higher lactate accumulation and lower fat oxidation during graded exercise in PASC; reviews describe a markedly reduced lactate threshold in PACVS too.[6,7,8] |
| Iron storage (ferritin index, transferrin saturation) | ↓ | Lipids, iron, thyroid & insulin markers | 61% of a PACVS registry cohort (n=191) had a low ferritin index with subnormal transferrin and transferrin saturation.[4] |
| Free T3 (tri-iodothyronine) | ↓ | Lipids, iron, thyroid & insulin markers | Low or low-normal in >80% of a PACVS registry cohort (n=191).[4] |
| Neurofilament light chain (sNfL) | ↑ | Brain neurochemistry & neuronal injury | Above the 90th percentile in about 27-30% of a PACVS registry cohort (n=191).[4] |
References
- Patterson BK, Yogendra R, Francisco EB, et al.. Detection of S1 spike protein in CD16+ monocytes up to 245 days in SARS-CoV-2-negative post-COVID-19 vaccine syndrome (PCVS) individuals. Hum Vaccin Immunother 21:2494934, 2025. doi:10.1080/21645515.2025.2494934
- Mantovani M, Bellavite P, Fazio S, et al.. Autoantibodies Targeting G-Protein-Coupled Receptors and RAS-Related Molecules in Post-Acute COVID Vaccination Syndrome: A Retrospective Case Series Study. Biomedicines 12:2852, 2024. doi:10.3390/biomedicines12122852
- Halma M, Varon J. Restoring trust in vaccination: listening to patients and acknowledging Post-Acute COVID Vaccine Syndrome. Front Med (Lausanne) 12:1688170, 2025. doi:10.3389/fmed.2025.1688170
- Mundorf AK, Semmler A, Heidecke H, et al.. Clinical and Diagnostic Features of Post-Acute COVID-19 Vaccination Syndrome (PACVS). Vaccines (Basel) 12:790, 2024. doi:10.3390/vaccines12070790
- Federico M. The Immunologic Downsides Associated with the Powerful Translation of Current COVID-19 Vaccine mRNA Can Be Overcome by Mucosal Vaccines. Vaccines (Basel) 12:1281, 2024. doi:10.3390/vaccines12111281
- Guntur VP, Nemkov T, de Boer E, et al.. Signatures of Mitochondrial Dysfunction and Impaired Fatty Acid Metabolism in Plasma of Patients with Post-Acute Sequelae of COVID-19 (PASC). Metabolites 12:1026, 2022. doi:10.3390/metabo12111026
- Gracidas C, Levy R, Varon J, et al.. Lactate, Capnia, and Fat Oxidation as Therapeutic Axes for SARS-CoV-2 Spike Protein-Induced Sequelae. Horm Metab Res 58:90-102, 2026. doi:10.1055/a-2794-9646
- Halma M, Varon J. Metabolic modulation as a therapeutic strategy for post-acute vaccination syndrome (PACVS): A review of pathomechanisms and existing therapeutic components. Biomed Pharmacother 193:118864, 2025. doi:10.1016/j.biopha.2025.118864
This page is educational and does not provide medical advice. Consult a healthcare provider for diagnosis and treatment.