Long COVID Syndrome Prevalence in 2025 in an Integral Healthcare Consortium: Persistent and Transient Symptoms

BACKGROUND: Long COVID can persist for years, but little is known about its prevalence in relation to the number of infections. This study examines the prevalence of Long COVID in association with the number of infections and vaccination status. METHODS: We analyzed anonymized data on Long COVID cases and thrombotic events from March 2020, provided by the Data Analysis Control Department for the population assigned to the CST (192,651 at March 2025). Additionally, we evaluated responses from a specific Long COVID symptom survey distributed to the entire CST population (n=1871 respondents). Symptomatic patients suspected of having Long COVID underwent blood tests to exclude alternative diagnoses. RESULTS: The overall detected prevalence of Long COVID was 2.4‰, with higher frequency among women aged 30–59 years. The survey, combined with blood test, improved detection rates by 26.3%. Long COVID prevalence was 3-10 times higher in individuals with three or more infections than in those with only one recorded infection (based on survey/CST data, respectively). The absolute number of thrombotic events doubled from 2020 to 2024 (p<0.0000001), occurring in both vaccinated and unvaccinated individuals, as well as in those with prior COVID-19 infection. CONCLUSION: Our findings demonstrate a link between SARS-CoV-2 reinfection and Long COVID prevalence. Furthermore, we observed a significant post-pandemic increase in thrombotic events across all populations, regardless of vaccination status or documented prior COVID-19 infection. Results suggest that COVID diagnosis should continue in suspected cases and that healthcare workers attending respiratory patients should continue wearing protective masks.