Serological response to SARS-CoV- 2 in patients under immunomodulatory treatment for rheumatoid arthritis

ABSTRACT

Background/Purpose: To determine and compare the magnitude of humoral immune response after the first, second, and third and overall exposure to SARS-CoV- 2, either by natural infection or vaccination, between rheumatoid arthritis (RA) patients under various immunosuppressive treatments and healthy controls (HCs). Method(s) Blood samples from various time points before and after the COVID-19 pandemic and longitudinal data on exposure history were obtained from RA patients and HCs recruited for this study. Antibody levels were then determined using indirect ELISA and statistically analysed in relation to exposure history. Result(s) A significant rise in antibody levels after overall exposure to SARS-CoV- 2 in RA patients and HCs was found, with no significant difference between the two groups. Amongst RA patients, a progressive rise in antibodies following each exposure to SARS-CoV- 2 was found, with antibody levels rising above the cut-off for seropositivity following the second and third exposures. Incidentally, HCs, despite having high antibody levels following the first and second exposure, were found to have antibody levels below the cut-off for seropositivity upon their third exposure to SARS-CoV- 2. Conclusion(s) Contrary to popular belief, RA patients, despite under immunosuppressive treatments, are capable of eliciting a humoral response that is comparable to that of healthy individuals. The lower antibody levels found in HCs by third exposure could signify that more vaccine boosters may be required to increase the public's immunity against SARS-CoV- 2 for herd immunity and avoid creating a reservoir for the emergence of novel variants with persistent infections.