Comparison of anti-SARS-CoV-2 IgG seropositivity among vaccinated, unvaccinated, and COVID-19 survivor individuals: A cross-sectional study in Palembang, Indonesia

Measurement of anti–severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
immunoglobulin G (IgG) antibody levels provides evidence of prior infection or
vaccination. Persistent vaccine hesitancy underscores the importance of robust, evidencebased
data to inform policy decisions. The aim of this study was to compare anti-SARSCoV-
2 IgG seropositivity among vaccinated individuals, unvaccinated individuals, and
coronavirus disease 2019 (COVID-19) survivors in the community during the pandemic.
In this cross-sectional study, 517 participants were enrolled, including 167 vaccinated
individuals, 97 COVID-19 survivors, and 253 unvaccinated individuals, selected through
multistage cluster sampling of 40 clusters. Anti-SARS-CoV-2 IgG seropositivity was
defined as ≥50 AU/mL. Multivariable logistic regression was performed to evaluate
associations between group type and seropositivity, adjusting for demographic factors,
COVID-19 symptoms, hypertension, and body mass index (BMI). Vaccinated individuals
demonstrated significantly higher odds of seropositivity compared with unvaccinated
participants (odds ratio (OR)=5.60; 95% confidence interval (CI): 2.36–13.27). Covariates
independently associated with seropositivity (p<0.05) included the presence of COVID-
19 symptoms, hypertension, and BMI. Vaccination was strongly associated with increased
anti-SARS-CoV-2 IgG seropositivity in the community, independent of clinical and
demographic factors. These findings support ongoing vaccination campaigns and
highlight the relevance of comorbidities and symptomatic history in shaping humoral
immune responses.