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Life span of Covid-19 antibodies following infection in a sample worker population in Qatar


 Background: COVID-19 antibodies’ longevity following infection is still unclear. Early data brought hope that acquired immunity was possible but subsequent studies suggested that immune protection might be short-lived. The results of recent studies provide greater insight into the human immune response to COVID-19. The Qatar Gas medical department’s strategy in preventing spread of infection among offshore and onshore workers consisted of maximizing the opportunities for COVID-19 polymerise chain reaction (PCR) and antibody testing. A large amount of data revealing the possible lifespan of COVID-19 antibodies in the study population was collected. Methods: Out of hundreds of employees who volunteered in this study about seroprevalance of COVID-19 antibodies, 52 whose results were reactive were tested for COVID-19 PCR before being selected. Employees with reactive or inconclusive PCR test results were excluded. Age, medical/surgical/social history, apart from past COVID-19 infection, were not selection criteria. We measured the period of time between the date of diagnosis and the antibody test result, segregating those still reactive from those who tested non-reactive at any point in time. The reactive group were retested for antibodies every 90 days as long as results continued to be reactive. Any cured employee was retested if they developed symptoms or was exposed to a confirmed positive case, to rule out the possibility of re-infection during this timeframe. Results: Only one employee was non-reactive after 110 days of COVID-19 PCR positive test result. 22 employees tested reactive although their PCR result had been negative. 30 employees tested reactive after a positive PCR with an average duration of 145 days, the shortest and longest being 24 and 223 respectively. Conclusion: We determined that antibodies’ longevity may extend to more than 6 months following COVID-19 infection and that there may be an early decay of antibodies in a limited proportion of the population, however further studies are recommended on larger populations. We noticed no cases of COVID-19 reinfection.