Abstract
BACKGROUND: A reliable marker of COVID-19 past infection is the anti-spike IgG antibody (Ab) titer of the SARS-CoV-2 virus, which may be identified even one year from diagnosis. Serology can be effective in diagnosing asymptomatic infection and patients with negative reverse transcription polymerase chain reaction. Exploring these dynamics and the persistence of antibodies is vital to understanding the disease process. MATERIALS AND METHODS: We designed this observational study to compare the seroconversion status of COVID-19 patients to healthy healthcare workers. The total number of participants was 272, including 58 hospitalized (recovered) patients, 153 healthcare workers (HCWs), and 61 control populations from the community. A total of 404 samples were taken for IgG titer measurements using the enzyme-linked immunosorbent assay method. RESULTS: Among 58 COVID-19 patients, 58.6% were men, and the male-to-female ratio was 1:1.41. All hospitalized patients had three months of persistence of Ab titer. The median IgG titer (interquartile range) optical density values for the hospitalized severe group on day 0, as well as during the fourth, eighth, and twelfth weeks, were 9.25 (6.01-11.893), 8.95 (5.52-12.42), 13.19 (12.26-13.26), and 12.99 (9.23-13.24), respectively. In comparison, the nonsevere group exhibited median values of 4.19 (3.08-9.89), 6.99 (4.32-9.75), 8.65 (5.83-13.08), and 12.48 (7.88-13.16), respectively. However, seroprevalence was higher in the control group (83.3%); in the HCWs, it was 54.9%. Although patients with severe disease had higher antispike IgG titers, no difference in titers was seen among age, gender, body mass index, or diabetes subgroups. CONCLUSION: We observed Ab titer persistence up to three months in cases of COVID-19-recovered patients, whereas seroprevalence was high among HCWs and the control group during the Delta wave.