Dinç, HARİKA ÖYKÜDemirci, MehmetÖzdemir, Yusuf EmreSirekbasan, SerhatAktaş, Ayse NurKaraali, RıdvanTuyji Tok, YeşimÖzbey, DoğukanAkçin, RüveydaGareayaghi, NesrinKuşkucu, Mert AhmetMidilli, KenanAygün, GökhanSarıbaş, SuatKocazeybek, Bekir2022-05-052022-05-052022-04-05http://hdl.handle.net/20.500.12645/30570Background: Monitoring the longevity of immunoglobulin G (IgG) responses following severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infections is vital to understanding the role of antibodies in preventing infection. Aims: To determine the quantitative IgG responses specific to the Spike-S1 (S1) receptor-binding domain (S1/RBD) region of the virus in serum samples taken between 4 weeks and 7 months after polymerase chain reaction (PCR) positivity in patients who are diagnosed with coronavirus disease-2019 (COVID-19). Study design: A longitudinal study. Methods: This study included 113 patients with a clinical and molecular diagnosis of COVID-19. The first and second serum samples were taken 1 and 7 months, respectively, after the PCR positivity. S1/RBD-specific IgG antibody response was assayed using anti-SARS-CoV- 2 QuantiVac ELISA (IgG) kit (Euroimmun, Lübeck, Germany). The neutralizing antibodies were investigated in 57 patients whose IgG test results were above the cut-off value. Results: In 57 patients with SARS-CoV-2 IgG, the anti-SARS-CoV-2 IgG quantitative antibody levels significantly decreased after 7 months (Z = −2.197, p = 0.028). A correlation was detected between the anti-SARS-CoV-2 IgG and nAb percent inhibition (IH%) levels detected in 1 month (rs = 0.496, p < 0.001), but without significant correlation in serum samples taken on 7 months. The nAb IH% levels of the first and second were compared for COVID-19 severity and revealed no statistical difference (p = 0.256). In the second serum sample, the nAb IH%s of patients with moderate COVID-19 showed a statistically significant difference from patients with mild COVID-19 (p = 0.018), but without significant differences between severe and moderate or mild COVID-19. Conclusion: SARS-CoV-2 quantitative IgG antibody titers are significantly reduced at long-term follow-up (> 6 months). Due to the limited information on seroconversion, comprehensive studies should be conducted for long-term follow-up of the immune response against SARS-CoV-2.info:eu-repo/semantics/openAccessCOVID-19SARS-CoV-2Neutralizing antibodyArticleWOS:0008060793000028513101888310.4274/balkanmedj.galenos.2022.2021-8-13135378574