Circulating IgG Levels in SARS-CoV-2 Convalescent Individuals in Cyprus

Area of Science:

• Immunology
• Virology
• Epidemiology

Background:

• Long-term humoral immunity and antibody response heterogeneity to SARS-CoV-2 require further investigation.
• Understanding antibody persistence is crucial for managing the COVID-19 pandemic and developing effective vaccines.

Purpose of the Study:

• To investigate the production and long-term persistence of circulating immunoglobulin G (IgG) antibodies against SARS-CoV-2 in individuals with a history of infection in Cyprus.
• To evaluate the association between antibody levels and demographic and clinical factors.

Main Methods:

• Serum samples from 969 unvaccinated individuals with reported SARS-CoV-2 infection were analyzed for receptor binding domain (RBD)-specific IgG antibodies using Abbott assays.
• Antibody levels were correlated with participant demographics (age, gender) and clinical data (symptoms, hospitalization).
• Statistical analyses were performed using Stata 16.

Main Results:

• Median RBD-specific IgG levels were 432.1 arbitrary units (AI)/mL, showing significant variability.
• Higher antibody levels were observed in older participants, males, and those with reported symptoms or hospitalization.
• RBD-specific IgG levels peaked at three months post-symptom onset, followed by a decrease up to six months and a slower decay thereafter.

Conclusions:

• SARS-CoV-2 IgG antibody response is bi-phasic with considerable titer variability.
• IgG levels are significantly associated with age, gender, and symptom severity in the studied population.
• These findings contribute to understanding long-term immunity following SARS-CoV-2 infection.