Evaluation of SARS-CoV-2 seroprevalence among clinical laboratory workers and its association with past exposure to infection and vaccination

Abstract

The pandemic of COVID-19, due to the SARS-CoV-2 virus, has significantly impacted global health. Understanding the dynamics of immunity, both natural and vaccine-induced, is crucial for public health strategies. The study aimed to determine the seroprevalence of SARS-CoV-2 antibodies among clinical laboratory workers and its relationship with previous exposure to infection and vaccination. This was a prospective observational study conducted at the chemical Pathology section of  Dow Diagnostic Research and Reference Laboratory (DDRRL), Dow University of Health Sciences, Karachi, Sindh, Pakistan from 1^st  January to 30^th December 2021. Following ethical approval, 80 clinical laboratory workers provided informed consent to participate. Blood samples were collected and tested for SARS-CoV-2 IgG antibodies. The baseline demographic and clinical information was recorded, and conducted follow-up antibody tests six months later. The mean age of the participants was 37.7 years, with a standard deviation of 9.42. There were 46 males (57.5%) and 34 females (42.5%) in the study. Half of the participants (50%) had been vaccinated, with 35% receiving a single dose and 15% receiving both doses. 71.3% of the participants had comorbidities. SARS-CoV-2 antibodies were found to be reactive in 50% of the participants. The study also found significant associations between antibody presence and prior COVID-19 infection, vaccination status, contact history with COVID-19 patients, and prior history of hospitalization (p < 0.05). The study compared the initial and post-booster antibody levels among three groups of subjects (vaccinated, vaccinated with no prior COVID-19 infection, and non-vaccinated with prior COVID-19 infection), and found that antibody levels were significantly high in vaccinated subjects and non-vaccinated subjects with prior COVID-19 infection (p-value < 0.05). A significant difference was observed in antibody titers among subjects with prior history of vaccination and COVID-19 infection. In conclusion both natural infection and vaccination may induce antibodies against SARS-CoV-2 infection.