Seroprevalence of SARS-COV-2 Antibodies in Medical Staff, South-West of Iran

Introduction: Serological assay has critical role in defining immunity based on seroprevalence. Identifying the extend of seropositivity would determine the truly infected cases. Method: We conducted serologic testing for SARS-COV-2 antibodies in 492 health care workers (HCWs) before vaccination program in Shiraz, Iran (30 April 2020). Results: Based on job position, cases were divided into two categories: frontline staff (169, 34.34%) and non-front-line staff (323, 65.65%). Of all cases 40.65 were female and the rest of them were male. Mean age was estimated 47.97 ± 109.20 and 38.98 ± 8.76 in high risk and low risk population respectively (P = 0.1). In total 367 (74.59%) subjects reported to suffered at least one of the COVID-19 symptoms. More than half of cases (73.57) had history of COVID-19 disease within six months before this survey. No relation was seen between blood type and immunoglobulin positivity. Seropositivity prevalence in low risk and high-risk populations were estimated 8.0 (95% CI: 1.0-16.8) and 5.2(95% CI: 1.2-9.8) respectively. The immunoglobulin test for SARS-COV-2 revealed that 64 (64/492, 13%) and 37 (37/492, 7.52%) subjects had IgG and IgM antibodies against the virus. 14 (14/169, 8.28%) individuals who had IgM were frontline health workers, this is while 23 (14/323, 7.12%) were non front lineConclusion: The findings of this study imply that seropositivity was lower in non-frontline health care staff. Furthermore, there was no association between blood type and seropositivity. Therefore, the knowledge of antibody status may help into overcome fears in clinical staff, and also more attention is need for interpreting the levels of anti-SARS-CoV-2 antibodies to make a clinical diagnosis of COVID-19, since the time of expose and time of test is an important point which should be considered in the issue.