Abstract
Post-COVID-19 Vaccination Syndrome (PCVS) refers to persistent, multisystemic symptoms developing after SARS-CoV-2 immunization. We established a nationwide registry across 14 Japanese outpatient clinics and analyzed 179 “clinically definitive” cases from 279 enrollees (December 2020–August 2023). All adverse events (AEs) were coded using MedDRA/J Preferred Terms and System Organ Classes; severity followed NCI-CTCAE V5.0. The cohort (66.5% female; mean age 59 years) experienced 493 AEs (median 2 per patient, range 1–29). Three System Organ Classes—General Disorders (29.2%), Nervous System Disorders (22.3%), and Musculoskeletal Disorders (10.1%)—accounted for 61.7% of events; fatigue, brain fog, dizziness, and extremity pain predominated. While 69.4% of AEs arose within 90 days post-vaccination, 12.4% appeared ≥ 360 days later. Severe AEs (≥ Grade 3) occurred in 14.6% of patients; overall improvement was 65.1%, leaving 29.4% unresolved. A provisional phenotype classification combining symptom patterns, onset timing, and severity identified high-risk subgroups with > 60% non-recovery rates. These findings underscore the need for enhanced post-vaccination surveillance systems and comprehensive care frameworks specifically tailored to address the protean manifestations and persistent nature of PCVS.
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Acknowledgements
The authors wish to extend their profound appreciation to the following esteemed physicians at the collaborating institutions for their invaluable support and contributions to the present study, entitled “Establishing a Registry for Post-COVID-19 Vaccination Syndromes and Comprehensive Analysis of COVID-19 Vaccine-Related Outcomes.” Their dedication and expertise were instrumental in the successful execution of this research. Dr. Takao Ikezawa (Ikezawa Women’s Health Clinic), Dr. Masato Yoshino (Kamata Yoshino Medical Clinic), Dr. Seiji Koide (Koide Clini), Dr. Iwao Sasaki and Dr. Minori Sasaki (Osaka Proctology Medical Clinic), Dr. Michio Suda (Koseido Medical Corporation, Suda Clinic), Dr. Toshiko Kamihata (Kamihata ENT Clinic), Dr. Hisashi Koshio (Koshio Orthopedics Clinic), Dr. Masahiro Kida (Kidasanyakudo Medical Clinic), Dr. Yuki Kobayashi and Dr. Shigeyuki Kobayashi (Kobayashi Clinic), Dr. Hideki Hashimoto (Fushimi Keimei Orthopedic & Osteoporosis Clinic of Sapporo), Dr. Masafumi Nakagawa (Otofuke ENT Clinic), Dr. Mutsuo Naganuma (Tokachi Mutsumino Medical Clinic).
The authors acknowledge the use of artificial intelligence tools, specifically Claude (Anthropic) and ChatGPT (OpenAI), for assistance with manuscript preparation and language refinement. All AI-generated content was carefully reviewed and validated by the authors to ensure scientific accuracy and appropriateness.
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AF, EN, and MF designed the study. AK, EO, MM, and YH performed the formal statistical analysis. AF, SK, NK, JU, EN, and MF interpreted the data. AF wrote the first draft of the manuscript. All authors contributed to the critical revision of the manuscript. All the authors have read and approved the final version of the manuscript.
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Fujisawa, A., Kodama, S., Konishi, N. et al. Characterizing persistent Post-COVID-19 vaccination symptoms using MedDRA system organ class and preferred term classifications. Sci Rep (2026). https://doi.org/10.1038/s41598-026-43949-z
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DOI: https://doi.org/10.1038/s41598-026-43949-z