Key Predictors of IgG Seropositivity in Individuals Exposed to SARS-CoV-2 Prior to Vaccine Rollout

Introduction: The COVID-19 pandemic has highlighted the need to understand factors influencing the immune response to SARS-CoV-2. Immunoglobulin G (IgG) antibodies serve as indicators of prior exposure and potential immunity. This study aims to identify demographic, clinical, and exposure-related predictors of IgG positivity in individuals exposed to SARS-CoV-2 before the initiation of vaccination programs. Materials and Methods: A cross-sectional study was conducted among 944 participants recruited from healthcare facilities. Eligible participants were aged 18 years or older, presented with COVID-19 symptoms or known exposure to confirmed SARS-CoV-2 cases, and had not received a COVID-19 vaccine. Data were collected via structured questionnaires, including demographics, clinical symptoms, and exposure history, and analyzed using logistic regression. IgG antibodies were detected using the SARS-CoV-2 IgG ELISA method. Results: IgG antibodies were detected in 75.0% of participants. Younger age (B = -0.026, p < 0.001), divorced marital status (B = 0.973, p = 0.021, Exp(B) = 2.65), recent international travel (B = 0.953, p = 0.047, Exp(B) = 2.594), and symptoms such as runny nose (B = 2.561, p = 0.012, Exp(B) = 12.96), nausea (B = 1.614, p = 0.048, Exp(B) = 5.025), and lack of appetite (B = 1.366, p = 0.049, Exp(B) = 3.918) were significant predictors of IgG positivity. Each additional year of age was associated with a 2.6% reduction in the likelihood of IgG positivity. The model achieved 75.4% classification accuracy with an AUC of 0.640, indicating moderate predictive performance. Conclusion: This study demonstrates the importance of demographic, clinical, and exposure-related factors in predicting IgG positivity. The findings enhance understanding of immune responses to SARS-CoV-2 and provide insights that can guide public health strategies in mitigating the pandemic's impact.