{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,13]],"date-time":"2026-04-13T11:56:07Z","timestamp":1776081367811,"version":"3.50.1"},"reference-count":66,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2026,4,13]],"date-time":"2026-04-13T00:00:00Z","timestamp":1776038400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["JCM"],"abstract":"<jats:p>Background: Post-exertional malaise (PEM), which is the cardinal feature of myalgic encephalomyelitis\/chronic fatigue syndrome (ME\/CFS), is also reported in a proportion of patients with post-COVID-19 syndrome (PCS). Our objective was to identify determinants that may be linked to the emergence of PEM in PCS patients. Methods: Patients fulfilling the World Health Organization definition for PCS who attended the post-COVID unit of the Internal Medicine Department of Angers University Hospital, France, between June 2020 and December 2023 were included retrospectively. Their medical records were reviewed to extract information on COVID-19 infection history, characteristics of post-exertional malaise (PEM), fatigue severity, and relevant epidemiological variables. Results: The study included 220 patients, grouped according to whether post-exertional malaise was present (PCS\/PEM+) or absent (PCS\/PEM\u2013). PEM was observed in 26.4% of patients and was significantly linked to earlier COVID onset in 2020\/2021 (OR 5.68 (95% CI: 1.66\u201319.45), p = 0.006), as well as higher fatigue levels (OR 2.07 (95% CI: 1.22\u20133.50), p = 0.007). Conclusions: Patients who contracted COVID-19 during the pre-Omicron period reported PEM more frequently than those infected in later waves. This observation could reflect differences in viral characteristics following the emergence of the Omicron variant; however, alternative explanations\u2014such as increasing vaccination coverage, accumulating post-infectious immunity, or other unmeasured factors\u2014cannot be ruled out. Based on the observed link between PEM and symptom severity, PCS patients should be systematically assessed for the presence of PEM.<\/jats:p>","DOI":"10.3390\/jcm15082948","type":"journal-article","created":{"date-parts":[[2026,4,13]],"date-time":"2026-04-13T10:19:14Z","timestamp":1776075554000},"page":"2948","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Post-Exertional Malaise in Post-COVID-19 Syndrome: A Shift in the Frequency Across Pandemic Phases"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2040-3387","authenticated-orcid":false,"given":"Alaa","family":"Ghali","sequence":"first","affiliation":[{"name":"Outpatient Department, Doue-En-Anjou Hospital, F-49700 Doue-En-Anjou, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2538-0076","authenticated-orcid":false,"given":"Christian","family":"Lavigne","sequence":"additional","affiliation":[{"name":"Department of Internal Medicine and Clinical Immunology, Angers University Hospital, F-49100 Angers, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Maria","family":"Ghali","sequence":"additional","affiliation":[{"name":"Department of General Medicine, University of Angers, F-49000 Angers, France"},{"name":"POPS, SFR ICAT, University of Angers, F-49000 Angers, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7184-752X","authenticated-orcid":false,"given":"Valentin","family":"Lacombe","sequence":"additional","affiliation":[{"name":"Department of Internal and Polyvalent Medicine, Haut-Anjou Hospital, F-53200 Chateau-Gontier, France"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,4,13]]},"reference":[{"key":"ref_1","unstructured":"(2022, March 11). A Clinical Case Definition of Post COVID-19 Condition by a Delphi Consensus. Available online: https:\/\/www.who.int\/publications-detail-redirect\/WHO-2019-nCoV-Post_COVID-19_condition-Clinical_case_definition-2021.1."},{"key":"ref_2","unstructured":"(2022, March 09). Post COVID-19 Condition (Long COVID). Available online: https:\/\/www.who.int\/srilanka\/news\/detail\/16-10-2021-post-covid-19-condition."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"ofac464","DOI":"10.1093\/ofid\/ofac464","article-title":"Risk of Long COVID in People Infected With Severe Acute Respiratory Syndrome Coronavirus 2 After 2 Doses of a Coronavirus Disease 2019 Vaccine: Community-Based, Matched Cohort Study","volume":"9","author":"Ayoubkhani","year":"2022","journal-title":"Open Forum Infect. Dis."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"101019","DOI":"10.1016\/j.eclinm.2021.101019","article-title":"Characterizing long COVID in an international cohort: 7 months of symptoms and their impact","volume":"38","author":"Davis","year":"2021","journal-title":"EClinicalMedicine"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"7","DOI":"10.1300\/J092v11n01_02","article-title":"Myalgic Encephalomyelitis\/Chronic Fatigue Syndrome: Clinical Working Case Definition, Diagnostic and Treatment Protocols","volume":"11","author":"Carruthers","year":"2003","journal-title":"J. Chronic Fatigue Syndr."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"327","DOI":"10.1111\/j.1365-2796.2011.02428.x","article-title":"Myalgic encephalomyelitis: International Consensus Criteria","volume":"270","author":"Carruthers","year":"2011","journal-title":"J. Intern. Med."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"e005798","DOI":"10.1136\/bmjopen-2014-005798","article-title":"Longitudinal follow-up of employment status in patients with chronic fatigue syndrome after mononucleosis","volume":"4","author":"Nyland","year":"2014","journal-title":"BMJ Open"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"35","DOI":"10.5014\/ajot.58.1.35","article-title":"Quality of life and symptom severity for individuals with chronic fatigue syndrome: Findings from a randomized clinical trial","volume":"58","author":"Taylor","year":"2004","journal-title":"Am. J. Occup. Ther. Off. Publ. Am. Occup. Ther. Assoc."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1","DOI":"10.7326\/0003-4819-102-1-","article-title":"Evidence for Active Epstein-Barr Virus Infection in Patients with Persistent, Unexplained Illnesses: Elevated Anti-Early Antigen Antibodies","volume":"102","author":"Jones","year":"1985","journal-title":"Ann. Intern. Med. Am. Coll. Physicians"},{"key":"ref_10","first-page":"204993612110093","article-title":"COVID-19 and post-infectious myalgic encephalomyelitis\/chronic fatigue syndrome: A narrative review","volume":"8","author":"Poenaru","year":"2021","journal-title":"Ther. Adv. Infect. Dis."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"639","DOI":"10.1080\/1744666X.2019.1596800","article-title":"Recent advances in our understanding of mast cell activation\u2013or should it be mast cell mediator disorders?","volume":"15","author":"Theoharides","year":"2019","journal-title":"Expert Rev. Clin. Immunol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1288","DOI":"10.1111\/all.15188","article-title":"Mast cell activation is associated with post-acute COVID-19 syndrome","volume":"77","author":"Wechsler","year":"2022","journal-title":"Allergy"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"693","DOI":"10.1159\/000524532","article-title":"Mast Cell Activation Syndromes: Collegium Internationale Allergologicum Update 2022","volume":"183","author":"Valent","year":"2022","journal-title":"Int. Arch. Allergy Immunol."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"961","DOI":"10.1093\/qjmed\/hcn123","article-title":"Postural orthostatic tachycardia syndrome is an under-recognized condition in chronic fatigue syndrome","volume":"101","author":"Hoad","year":"2008","journal-title":"QJM Mon. J. Assoc. Physicians"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"573","DOI":"10.1016\/j.jaccas.2021.01.009","article-title":"Long-Haul Post\u2013COVID-19 Symptoms Presenting as a Variant of Postural Orthostatic Tachycardia Syndrome","volume":"3","author":"Johansson","year":"2021","journal-title":"JACC Case Rep."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"e2024358118","DOI":"10.1073\/pnas.2024358118","article-title":"Redox imbalance links COVID-19 and myalgic encephalomyelitis\/chronic fatigue syndrome","volume":"118","author":"Paul","year":"2021","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Townsend, L., Dyer, A.H., Jones, K., Dunne, J., Mooney, A., Gaffney, F., O\u2019Connor, L., Leavy, D., O\u2019Brien, K., and Dowds, J. (2020). Persistent fatigue following SARS-CoV-2 infection is common and independent of severity of initial infection. PLoS ONE, 15.","DOI":"10.1371\/journal.pone.0240784"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"375","DOI":"10.1186\/s12967-023-04229-w","article-title":"The relevance of pacing strategies in managing symptoms of post-COVID-19 syndrome","volume":"21","author":"Ghali","year":"2023","journal-title":"J. Transl. Med."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Petracek, L.S., Suskauer, S.J., Vickers, R.F., Patel, N.R., Violand, R.L., Swope, R.L., and Rowe, P.C. (2021). Adolescent and Young Adult ME\/CFS After Confirmed or Probable COVID-19. Front. Med., 8.","DOI":"10.3389\/fmed.2021.668944"},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"(2015). Beyond Myalgic Encephalomyelitis\/Chronic Fatigue Syndrome: Redefining an Illness. Mil. Med., 180, 721\u2013723.","DOI":"10.7205\/MILMED-D-15-00085"},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Ghali, A., Lacout, C., Ghali, M., Gury, A., Delattre, E., Lavigne, C., and Urbanski, G. (2021). Warning Signals of Post-Exertional Malaise in Myalgic Encephalomyelitis\/Chronic Fatigue Syndrome: A Retrospective Analysis of 197 Patients. J. Clin. Med., 10.","DOI":"10.3390\/jcm10112517"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1121","DOI":"10.1001\/archneur.1989.00520460115022","article-title":"The Fatigue Severity Scale: Application to Patients With Multiple Sclerosis and Systemic Lupus Erythematosus","volume":"46","author":"Krupp","year":"1989","journal-title":"Arch. Neurol."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"114","DOI":"10.1111\/j.1468-1331.2010.03090.x","article-title":"Fatigue in multiple sclerosis: Associations with health-related quality of life and physical performance","volume":"18","author":"Smedal","year":"2011","journal-title":"Eur. J. Neurol."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"3","DOI":"10.1016\/j.autneu.2018.02.005","article-title":"Postural Tachycardia Syndrome\u2013Diagnosis, Physiology, and Prognosis","volume":"215","author":"Arnold","year":"2018","journal-title":"Auton. Neurosci. Basic Clin."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"69","DOI":"10.1007\/s10286-011-0119-5","article-title":"Consensus statement on the definition of orthostatic hypotension, neurally mediated syncope and the postural tachycardia syndrome","volume":"21","author":"Freeman","year":"2011","journal-title":"Clin. Auton. Res."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"e2455430","DOI":"10.1001\/jamanetworkopen.2024.55430","article-title":"Sex Differences in Long COVID","volume":"8","author":"Shah","year":"2025","journal-title":"JAMA Netw. Open"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Kokolevich, Z.M., Crowe, M., Mendez, D., Biros, E., and Reznik, J.E. (2022). Most Common Long COVID Physical Symptoms in Working Age Adults Who Experienced Mild COVID-19 Infection: A Scoping Review. Healthcare, 10.","DOI":"10.3390\/healthcare10122577"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"1706","DOI":"10.1038\/s41591-022-01909-w","article-title":"Symptoms and risk factors for long COVID in non-hospitalized adults","volume":"28","author":"Subramanian","year":"2022","journal-title":"Nat. Med."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1085","DOI":"10.1007\/s11606-024-09290-9","article-title":"Incidence and Prevalence of Post-COVID-19 Myalgic Encephalomyelitis: A Report from the Observational RECOVER-Adult Study","volume":"40","author":"Vernon","year":"2025","journal-title":"J. Gen. Intern. Med."},{"key":"ref_30","first-page":"e44888","article-title":"The Burden and Characteristics of Post-COVID-19 Conditions Among Laboratory-Confirmed Delta and Omicron COVID-19 Cases: A Preliminary Study From Maharashtra, India","volume":"15","author":"Karyakarte","year":"2023","journal-title":"Cureus"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"5104","DOI":"10.1038\/s41467-022-32507-6","article-title":"A prospective observational study of post-COVID-19 chronic fatigue syndrome following the first pandemic wave in Germany and biomarkers associated with symptom severity","volume":"13","author":"Kedor","year":"2022","journal-title":"Nat. Commun."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"191","DOI":"10.1186\/s12967-024-04979-1","article-title":"Fatigue and symptom-based clusters in post COVID-19 patients: A multicentre, prospective, observational cohort study","volume":"22","author":"Cornelissen","year":"2024","journal-title":"J. Transl. Med."},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Bonilla, H., Quach, T.C., Tiwari, A., Bonilla, A.E., Miglis, M., Yang, P.C., Eggert, L.E., Sharifi, H., Horomanski, A., and Subramanian, A. (2023). Myalgic Encephalomyelitis\/Chronic Fatigue Syndrome is common in post-acute sequelae of SARS-CoV-2 infection (PASC): Results from a post-COVID-19 multidisciplinary clinic. Front. Neurol., 14.","DOI":"10.3389\/fneur.2023.1090747"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"pzac005","DOI":"10.1093\/ptj\/pzac005","article-title":"Chronic Fatigue and Postexertional Malaise in People Living With Long COVID: An Observational Study","volume":"102","author":"Twomey","year":"2022","journal-title":"Phys. Ther."},{"key":"ref_35","doi-asserted-by":"crossref","unstructured":"Peter, R.S., Nieters, A., G\u00f6pel, S., Merle, U., Steinacker, J.M., Deibert, P., Friedmann-Bette, B., Nie\u00df, A., M\u00fcller, B., and Schilling, C. (2025). Persistent symptoms and clinical findings in adults with post-acute sequelae of COVID-19\/post-COVID-19 syndrome in the second year after acute infection: A population-based, nested case-control study. PLoS Med., 22.","DOI":"10.1371\/journal.pmed.1004511"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"179","DOI":"10.1111\/joim.12564","article-title":"Postural orthostatic tachycardia is not a useful diagnostic marker for chronic fatigue syndrome","volume":"281","author":"Roerink","year":"2017","journal-title":"J. Intern. Med."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"205","DOI":"10.1007\/s12026-021-09185-5","article-title":"Postural orthostatic tachycardia syndrome (POTS) and other autonomic disorders after COVID-19 infection: A case series of 20 patients","volume":"69","author":"Blitshteyn","year":"2021","journal-title":"Immunol. Res."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"1880","DOI":"10.1016\/j.hrthm.2022.07.014","article-title":"Postural orthostatic tachycardia syndrome as a sequela of COVID-19","volume":"19","author":"Ormiston","year":"2022","journal-title":"Heart Rhythm"},{"key":"ref_39","first-page":"e013629","article-title":"Prevalence and Clinical Impact of Postural Orthostatic Tachycardia Syndrome in Highly Symptomatic Long COVID","volume":"18","author":"Wijnbladh","year":"2025","journal-title":"Circ. Arrhythm. Electrophysiol."},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Isaac, R., Corrado, J., and Sivan, M. (2023). Detecting Orthostatic Intolerance in Long COVID in a Clinic Setting. Int. J. Environ. Res. Public. Health, 20.","DOI":"10.3390\/ijerph20105804"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"e29486","DOI":"10.1002\/jmv.29486","article-title":"Prevalence of orthostatic intolerance in long covid clinic patients and healthy volunteers: A multicenter study","volume":"96","author":"Lee","year":"2024","journal-title":"J. Med. Virol."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"587","DOI":"10.1007\/s00415-021-10735-y","article-title":"Autonomic dysfunction in post-COVID patients with and witfhout neurological symptoms: A prospective multidomain observational study","volume":"269","author":"Furlanis","year":"2022","journal-title":"J. Neurol."},{"key":"ref_43","doi-asserted-by":"crossref","unstructured":"Huang, L., Li, H., He, B., Wang, X., Zhang, Q., and Peng, W. (2025). Prevalence of cardiovascular symptoms in post-acute COVID-19 syndrome: A meta-analysis. BMC Med., 23.","DOI":"10.1186\/s12916-025-03908-3"},{"key":"ref_44","doi-asserted-by":"crossref","unstructured":"Deroche, L., Bellecave, P., David, R., Ouattara, E., Garcia, M., Roblot, F., Boinot, L., Faucher, J.-F., Rejasse, A., and Gschwind, G. (2023). One year of SARS-CoV-2 circulation in the Nouvelle-Aquitaine region, February 2021\u20132022, France. Front. Microbiol., 14.","DOI":"10.3389\/fmicb.2023.1176575"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"e072529","DOI":"10.1136\/bmj-2022-072529","article-title":"Long covid outcomes at one year after mild SARS-CoV-2 infection: Nationwide cohort study","volume":"380","author":"Mizrahi","year":"2023","journal-title":"BMJ"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"1451","DOI":"10.1016\/j.amjmed.2021.07.004","article-title":"Post-COVID-19 Tachycardia Syndrome: A Distinct Phenotype of Post-Acute COVID-19 Syndrome","volume":"134","author":"Reistam","year":"2021","journal-title":"Am. J. Med."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"1029","DOI":"10.1016\/j.amjmed.2024.04.041","article-title":"Examining Well-Being and Cognitive Function in People With Long COVID and ME\/CFS, and Age-Matched Healthy Controls: A Case-Case-Control Study","volume":"138","author":"Mclaughlin","year":"2025","journal-title":"Am. J. Med."},{"key":"ref_48","doi-asserted-by":"crossref","unstructured":"Thi Khanh, H.N., Cornelissen, L., Castanares-Zapatero, D., De Pauw, R., Van Cauteren, D., Demarest, S., Drieskens, S., Devleesschauwer, B., De Ridder, K., and Charafeddine, R. (2023). Association between SARS-CoV-2 variants and post COVID-19 condition: Findings from a longitudinal cohort study in the Belgian adult population. BMC Infect. Dis., 23.","DOI":"10.1186\/s12879-023-08787-8"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"1934","DOI":"10.1001\/jama.2023.8823","article-title":"Development of a Definition of Postacute Sequelae of SARS-CoV-2 Infection","volume":"329","author":"Thaweethai","year":"2023","journal-title":"JAMA"},{"key":"ref_50","doi-asserted-by":"crossref","unstructured":"El-Akkad, S.-E.-D., Shao, S., Tran, K.C., Naik, H., Janjua, N., Sbihi, H., Carlsten, C., Russell, J.A., Levin, A., and Wong, A.W. (2025). Association between COVID-19 vaccination, SARS-CoV-2 variants, and post COVID-19 condition: A cross-sectional study. PLoS ONE, 20.","DOI":"10.1371\/journal.pone.0336929"},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"108522","DOI":"10.1016\/j.ijid.2026.108522","article-title":"Prevalence of Post-COVID Symptoms Across Variants of Concern and Follow-up Periods: A Systematic Review and Meta-Analysis","volume":"166","author":"Lugtu","year":"2026","journal-title":"Int. J. Infect. Dis."},{"key":"ref_52","doi-asserted-by":"crossref","unstructured":"Du, M., Ma, Y., Deng, J., Liu, M., and Liu, J. (2022). Comparison of Long COVID-19 Caused by Different SARS-CoV-2 Strains: A Systematic Review and Meta-Analysis. Int. J. Environ. Res. Public Health, 19.","DOI":"10.3390\/ijerph192316010"},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"1930","DOI":"10.1093\/cid\/ciad045","article-title":"Severe Fatigue and Persistent Symptoms at 3 Months Following Severe Acute Respiratory Syndrome Coronavirus 2 Infections During the Pre-Delta, Delta, and Omicron Time Periods: A Multicenter Prospective Cohort Study","volume":"76","author":"Gottlieb","year":"2023","journal-title":"Clin. Infect. Dis."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"194","DOI":"10.1093\/cid\/ciad143","article-title":"Post-Acute Sequelae After Severe Acute Respiratory Syndrome Coronavirus 2 Infection by Viral Variant and Vaccination Status: A Multicenter Cross-Sectional Study","volume":"77","author":"Kahlert","year":"2023","journal-title":"Clin. Infect. Dis."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"694","DOI":"10.1001\/jama.2024.24184","article-title":"2024 Update of the RECOVER-Adult Long COVID Research Index","volume":"333","author":"Geng","year":"2025","journal-title":"JAMA"},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"707","DOI":"10.1016\/S0140-6736(24)01136-X","article-title":"Long COVID: A clinical update","volume":"404","author":"Greenhalgh","year":"2024","journal-title":"Lancet"},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"1231","DOI":"10.1093\/infdis\/jiad236","article-title":"Intrinsic and Effective Severity of Coronavirus Disease 2019 Cases Infected With the Ancestral Strain and Omicron BA.2 Variant in Hong Kong","volume":"228","author":"Wong","year":"2023","journal-title":"J. Infect. Dis."},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"1783","DOI":"10.1016\/j.vaccine.2023.02.008","article-title":"Protective effect of COVID-19 vaccination against long COVID syndrome: A systematic review and meta-analysis","volume":"41","author":"Watanabe","year":"2023","journal-title":"Vaccine"},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"106358","DOI":"10.1016\/j.jinf.2024.106358","article-title":"The effect of pre-COVID and post-COVID vaccination on long COVID: A systematic review and meta-analysis","volume":"89","author":"Chow","year":"2024","journal-title":"J. Infect."},{"key":"ref_60","doi-asserted-by":"crossref","first-page":"e436","DOI":"10.1093\/cid\/ciaf549","article-title":"Effectiveness of COVID-19 Vaccination and Prior Infections to Reduce Long COVID Risk During the Pre-Omicron and Omicron Periods","volume":"82","author":"Carazo","year":"2026","journal-title":"Clin. Infect. Dis."},{"key":"ref_61","doi-asserted-by":"crossref","unstructured":"Kraus, T., Napierala, H., Schrimpf, A., Joos, S., Blaschke, S., Hanses, F., Vehreschild, M.J.G.T., Hamelmann, E., Schmidt, J., and Scheer, C.S. (2026). Impact of COVID-19 vaccination on post-COVID syndrome across clinical definitions and phenotypes: A prospective multicenter cohort study. Mayo Clin. Proc., Online ahead of print.","DOI":"10.1016\/j.mayocp.2026.02.018"},{"key":"ref_62","doi-asserted-by":"crossref","first-page":"515","DOI":"10.1056\/NEJMoa2403211","article-title":"Postacute Sequelae of SARS-CoV-2 Infection in the Pre-Delta, Delta, and Omicron Eras","volume":"391","author":"Xie","year":"2024","journal-title":"N. Engl. J. Med."},{"key":"ref_63","doi-asserted-by":"crossref","first-page":"124","DOI":"10.1186\/s40478-022-01426-4","article-title":"In vitro and in vivo differences in neurovirulence between D614G, Delta And Omicron BA.1 SARS-CoV-2 variants","volume":"10","author":"Bauer","year":"2022","journal-title":"Acta Neuropathol. Commun."},{"key":"ref_64","doi-asserted-by":"crossref","first-page":"105580","DOI":"10.1016\/j.antiviral.2023.105580","article-title":"SARS-CoV-2 Omicron (B.1.1.529) shows minimal neurotropism in a double-humanized mouse model","volume":"212","author":"Wang","year":"2023","journal-title":"Antivir. Res."},{"key":"ref_65","doi-asserted-by":"crossref","first-page":"297","DOI":"10.1007\/s10753-022-01734-w","article-title":"SARS-CoV-2 Variants Show a Gradual Declining Pathogenicity and Pro-Inflammatory Cytokine Stimulation, an Increasing Antigenic and Anti-Inflammatory Cytokine Induction, and Rising Structural Protein Instability: A Minimal Number Genome-Based Approach","volume":"46","author":"Barh","year":"2023","journal-title":"Inflammation"},{"key":"ref_66","doi-asserted-by":"crossref","unstructured":"Guo, Y., Han, J., Zhang, Y., He, J., Yu, W., Zhang, X., Wu, J., Zhang, S., Kong, Y., and Guo, Y. (2022). SARS-CoV-2 Omicron Variant: Epidemiological Features, Biological Characteristics, and Clinical Significance. Front. Immunol., 13.","DOI":"10.3389\/fimmu.2022.877101"}],"container-title":["Journal of Clinical Medicine"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2077-0383\/15\/8\/2948\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,4,13]],"date-time":"2026-04-13T11:05:16Z","timestamp":1776078316000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2077-0383\/15\/8\/2948"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,4,13]]},"references-count":66,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2026,4]]}},"alternative-id":["jcm15082948"],"URL":"https:\/\/doi.org\/10.3390\/jcm15082948","relation":{},"ISSN":["2077-0383"],"issn-type":[{"value":"2077-0383","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,4,13]]}}}