Seroconversion in COVID-19: a Tool for Risk Assessment in Frontline COVID Warriors

• Published in: Indian journal of clinical biochemistry Vol. 36; no. S1; p. S139
• Main Authors: Yadav, Charu, Singla, Sonam, Singh, Vyoma, Sarma, Smita, Vinayak, Kamini, Wadhwa, Teena, Saxena, Renu, Mehta, Yatin
• Format: Journal Article
• Language: English
• Published: Springer 24.05.2022
• Subjects: Health aspects; Immunoglobulin G; Infection; Risk assessment
• ISSN: 0970-1915

Objectives : To analyse the seroconversion rate of COVID-19 antibody and its association with risk of future infection in frontline COVID warriors. Methodology: Longitudinal cohort study conducted in 218 frontline COVID warriors. Baseline anti-spike IgG antibodies estimated and followed up for RT-PCR positive infection. Seropositive subjects were followed up with serial titres at 4 visits upto 6 months. Statistical analysis: SPSS ver. 22.0 used employing chi-square test for association of seropositivity with RT-PCR outcome. Antibody kinetics was calculated using a mathematical linear regression model. Incidence rate was calculated per 10000 person years at risk and relative risk was calculated. Results: IgG positivity was seen in 93.8% subjects who had COVID infection in past 30 days. Significantly higher incidence of infection was observed in seronegative subjects who were at 10 times higher risk of infection than seropositive cases (p<0.001). A sharp rise in infectivity was seen in August 2020 which declined after 2 months. Antibody titres peaked during 1.5-3 months followed by steep decline till 4th-5th month and gradual decline till 6 months. Only 2 asymptomatic cases turned seronegative by the end of study. Conclusion: Analysis of natural antibody response postulated a persistence of antibodies till 6 months post RT PCR confirmed infection. The seronegative subjects were 10 times more prone to COVID infection due to lack of innate immunity. Keywords : COVID IgG antibody, frontline COVID warriors, COVID-19 high risk group, immunity