Persistence of SARS-CoV-2 antibodies and symptoms in an Irish Healthcare Worker (HCW) setting: Results of the CAST Study

Abstract Objectives:This study examined the natural history, including incidence and prevalence, of SARS-CoV-2 antibodies serially up to 6 months post infection in Irish Healthcare Workers (HCW) at a large urban academic obstetric unit, during the first pandemic peak from March to September 2020. Design: This single centre observational study profiled SARS-CoV-2 incidence and infection rates using viral RNA detected using oro/naso-pharyngeal swabs accompanied by serological assessment of study participants for the presence of antibodies. Participant demographics were also collected alongside information on clinical symptoms and time to recovery. Real time polymerase-chain-reaction (RT-PCR) for viral RNA detection was performed using the Allplex SARS-CoV-2 platform (SeeGene Inc.,Rep. of Korea) or the GeneXpert SARS-CoV-2 platform (Cepheid, USA). Intravenous blood samples were obtained at the time of initial swab and at up to 4 time points thereafter, for the serological assessment of antibodies against both the spike and nucleocapsid protein antigens of SARS-CoV-2. Serological response was measured using the Captia; Anti-SARS-CoV-2 (IgG) ELISA (Trinity Biotech) as part of a clinical performance evaluation. Two other testing methods were also used; the Anti-SARS-CoV-2 ELISA (IgG) assay (EuroImmun) and the Abbott Anti-SARS-CoV-2 IgG 75 kit on the Architect i2000SR instrument (Abbott Laboratories). Setting: Academic Tertiary Maternity Hospital in Dublin, Ireland. Participants: We invited symptomatic and asymptomatic healthcare workers employed at the Rotunda Maternity Hospital to participate in the CAST study. Main Outcome Measures: The CAST study aimed to examine the infection rate and clinical symptoms of SARS-CoV-2 in HCWs and to determine the presence and longevity of antibodies in this group. We also sought to examine the clinical utility of the Captia; Anti-SARS-CoV-2 (IgG) ELISA (Trinity Biotech) and to compare it to the current accepted gold standard platform in Ireland. Results: By July 2020, 398 tests had been completed on symptomatic staff with clinical suspicion of SARS-CoV-2 infection. In this cohort, 14% (n=54/398) had detectable levels of SARS-CoV-2 RNA, indicating a positive diagnosis for Coronavirus disease 2019 (COVID-19). The CAST study enrolled 137 HCW, with 86 participants symptomatic at time of swab collection and a further 51 asymptomatic control participants. SARS-CoV-2 RNA was detected in 45/86 (52%) symptomatic study participants and serological positivity was confirmed in 44/45 (98%) of those participants. Asymptomatic SARS-CoV-2 RNA infection was detected in 2/51 control participants (4%), with a seropositivity rate in this group of 8% (4/51). We demonstrate that 95% of SARS-CoV-2 positive participants have detectable levels of antibodies at 100 days post infection, which persisted in 91% of participants at day 160+. Ongoing symptoms up to six months post infection were present in 50% of study participants with positive PCR and serology results. These data will be important to consider for long-term workforce planning in healthcare as the ongoing pandemic continues. Funding: The CAST study was supported by the Rotunda Hospital and Trinity Biotech.