Background: This study presents a unique investigation into the relationship between the persistence of IgG antibody levels and reinfection in recovered coronavirus disease 2019 (COVID-19) patients. By shedding light on this aspect, we aim to address concerns about the risk of reinfection in unvaccinated patients, offering a fresh perspective in the current COVID-19 research landscape. Objectives: This study takes a novel approach by focusing on the antibody response and reinfection in COVID-19 patients who were treated in outpatient settings for six months. This approach distinguishes our research within the broader context of COVID-19 studies. Methods: Our comprehensive and rigorous prospective cohort study included 149 COVID-19 outpatients referred to Imam Ali Clinic in Dezfoul City, Khuzestan province, Iran. Data was meticulously collected from September 2021 to February 2022. All unvaccinated patients underwent RT-PCR testing, and their anti-SARS-CoV-2 IgM/IgG levels were measured at the onset of illness. Serum IgG levels were then measured again after three and six months using ELISA. Results: All COVID-19 patients had their IgG antibody levels tested three times (on days two to four of the illness, at three months, and at six months). Significant differences in IgG antibody levels were observed between the vaccinated and unvaccinated groups during each period (P < 0.05). Additionally, there were substantial differences between the hypertension and non-hypertension groups (P = 0.032). Importantly, our findings reaffirm the impartiality of our research, as no significant differences were found between reinfection rates and various demographic or disease-related factors. Conclusions: The findings of this study suggest that high levels of IgG antibodies in unvaccinated patients could potentially reduce the risk of reinfection. This insight could have important implications for public health strategies and the management of COVID-19 in unvaccinated populations, providing valuable information for decision-makers in the field.
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