Objectives This study aimed to describe the impact of vaccination and the role of humoral responses on post–COVID-19 syndrome 1 year after the onset of SARS coronavirus type 2 (CoV-2). Methods This prospective study was conducted through interviews to investigate post–COVID-19 syndrome 6 and 12 months after disease onset in all adult in- and outpatients with COVID-19 at Udine Hospital (March–May 2020). Vaccination status and two different serological assays to distinguish between response to vaccination (receptor-binding domain (RBD) SARS-CoV-2 IgG) and/or natural infection (non-RBD-SARS-CoV-2 IgG) were also assessed. Results A total of 479 patients (52.6% female; mean age: 53 years) were interviewed 13.5 months (standard deviation: 0.6 months) after acute infection. Post–COVID-19 syndrome was observed in 47.2% of patients ( n = 226) after 1 year. There were no significant differences in the worsening of post–COVID-19 symptoms (22.7% vs. 15.8%; p = 0.209) among vaccinated ( n = 132) and unvaccinated ( n = 347) patients. The presence of non-RBD SARS-CoV-2 IgG induced by natural infection showed a significant association with post–COVID-19 syndrome (OR: 1.35; 95% CI, 1.11–1.64; p = 0.003), and median non-RBD SARS-CoV-2 IgG titres were significantly higher in long haulers than in patients without symptoms (22 kAU/L (interquartile range, 9.7–37.2 kAU/L) vs. 14.1 kAU/L (interquartile range, 5.4–31.3 kAU/L); p = 0.009) after 1 year. In contrast, the presence of RBD SARS-CoV-2 IgG was not associated with the occurrence of post–COVID-19 syndrome (>2500 U/mL vs. 0.9–2500 U/mL; OR: 1.36; 95% CI, 0.62–3.00; p = 0.441), and RBD SARS-CoV-2 IgG titres were similar in long haulers as in patients without symptoms (50% values > 2500 U/mL vs. 55.6% values > 2500 U/mL; p = 0.451). Discussion The SARS-CoV-2 vaccination is not associated with the emergence of post–COVID-19 symptoms more than 1 year after acute infection. The persistence of high serological titre response induced by natural infection, but not vaccination, may play a role in long-haul COVID-19. Graphical abstract Image 1
【저자키워드】 SARS-CoV-2 antibodies, Long COVID-19, COVID-19 vaccination, unvaccinated, SARS-CoV-2 serology, SARS-CoV-2 vaccination, Vaccinated, Hybrid immunity, natural immunity, Post–COVID-19, Post–COVID-19, 【초록키워드】 COVID-19, IgG, vaccination, Prospective Study, Symptom, Serological assay, Humoral response, RBD, persistence, acute infection, Patient, SARS Coronavirus, natural infection, serological, patients, SARS-CoV-2 IgG, association, Outpatient, Image, disease onset, Vaccination Status, interquartile range, Abstract, 95% CI, no significant difference, domain, worsening, syndrome, titre, objective, Occurrence, Result, conducted, median, significantly higher, response to vaccination, with COVID-19, without symptom, 【제목키워드】 Patient, association, humoral, syndrome,