A Two-Phase, Single Cohort Study of COVID-19 Antibody Sera-Surveillance

Abstract

Objective: The infectious corona virus, COVID-19 has high case mortality in those whom suffer with severe symptoms requiring hospitalisation. A major problem associated with COVID-19 is the spread of infection by a-symptomatic carriers, or those with mild symptoms. We aim to determine the antibody prevalence in a professional Welsh cohort and begin to explore the longevity of COVID-19 antibodies. Methods: 739 Cardiff Metropolitan University staff members took part in an observational study to determine the prevalence of COVID-19 antibodies in a two-phase, single cohort study. All participants were tested for IgM and IgG antibodies against COVID-19 using a lateral flow detection assay. Venous blood samples from positive participants and a randomly selected negative population were collected to confirm antibody titre, using two gold standard immunoassays, carried out independently by the Specialist Virology Centre, UHW. Results: 3.65% of the population tested positive for antibodies against COVID-19, with a higher prevalence seen in male participants (5% vs. 2.73% of females). In addition to gender, both pre-existing asthma and age were key determinants in antibody positivity. 78.26% retained antibodies at the 3 months follow up test. 36.36% of females lost antibody positivity between the 3 - and 6 - month time points compared with 8.3% of males. Lateral flow antibody testing was shown to have 96% sensitivity and 95% specificity compared with standard tests. Conclusion: We conclude that prevalence of COVID-19 antibodies is evident in the asymptomatic population, and in 78.26% of those initially antibody positive prevails at approximately 6 months from perceived time of exposure. Males are 4 times more likely to retain antibodies for longer than females.