ImportanceEarlier research on COVID-19 vaccines identified a range of adverse reactions related to proinflammatory actions that can lead to an excessive immune response and sustained inflammation. However, no study has been conducted on the association between inflammatory musculoskeletal disorders and COVID-19 vaccines.ObjectiveTo investigate the incidence rates of inflammatory musculoskeletal disorders following COVID-19 vaccination and to compare them with those of unvaccinated individuals.Design, Setting, and ParticipantsThis retrospective nationwide cohort study used data from the Korean National Health Insurance Service (NHIS) database, involving 2,218,715 individuals. Data were collected from January 1, 2021, to 12 weeks after the second dose of vaccine for vaccinated individuals and 12 weeks after September 30, 2021, for unvaccinated individuals.ExposuresStatus was categorized as unvaccinated and vaccinated with mRNA vaccine, viral vector vaccine, and mixing and matching.Main Outcomes and MeasuresThe primary outcome was the occurrence of inflammatory musculoskeletal disorders that were selected as plantar fasciitis (ICD code, M72.2), rotator cuff syndrome (M75.1), adhesive capsulitis (M75.0), herniated intervertebral disc (HIVD) (M50.2/M51.2), spondylosis (M47.9), bursitis (M71.9), Achilles tendinitis (M76.6), and de-Quervain tenosynovitis (M65.4). Multivariate logistic regression analysis was used to determine the risk factors of musculoskeletal disorders after adjusting for potential confounders.ResultsAmong the 2,218,715 individuals, 1,882,640 (84.9%) received two doses of the COVID-19 vaccine, and 336,075 (15.1%) did not. At 12 weeks after vaccination, the incidences of plantar fasciitis (0.14-0.17%), rotator cuff syndrome (0.29-0.42%), adhesive capsulitis (0.29-0.47%), HIVD (0.18-0.23%), spondylosis (0.14-0.23%), bursitis (0.02-0.03%), Achilles tendinitis (0.0-0.05%), and de-Quervain tenosynovitis (0.04-0.05%) were higher in all three vaccinated groups (mRNA, cDNA, and mixing and matching vaccines) when compared to the unvaccinated group. All COVID-19 vaccines were identified as significant risk factors for each inflammatory musculoskeletal disorder (odds ratio, 1.404-3.730), except for mixing and matching vaccines for de-Quervain tenosynovitis.Conclusions and RelevanceThis cohort study found that individuals who received any COVID-19 vaccine were more likely to be diagnosed with inflammatory musculoskeletal disorders than those who did not. This information will be useful in clarifying the adverse reactions to COVID-19 vaccines and informing people about their potential for inflammatory musculoskeletal disorders after vaccination.