Persistence of SARS-CoV-2 antibodies and symptoms in an Irish Healthcare Worker (HCW) setting: Results of the COVID Antibody Staff Testing (CAST) Study
Authors: Griffin Joanna , Tully Elizabeth , Cody Fiona , Edwards Katherine , Moran Kara , LeBlanc David , O’Loughlin John , McLoughlin Ruth , Cummins Rachel , Breen Sheila , Drew Richard , Natin Dominick , Malone Fergal 
Published: February 2021

AbstractObjectivesThis 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 (HCWs) at an academic tertiary maternity hospital, during the first pandemic peak from March to September 2020.DesignThis single centre observational study profiled SARS-CoV-2 incidence and infection using viral RNA detected using oro/nasopharyngeal swabs accompanied by serological assessment of study participants for the presence of S SARS-CoV-2 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 SARS-CoV-2 detection was performed using the Allplex™ SARS-CoV-2 three gene target 2019-nCoV assay (SeeGene Inc., Rep. of Korea) or the Xpert Xpress SARS-CoV-2 assay on the GeneXpert platform (Cepheid, USA). 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).SettingAcademic Tertiary Maternity Hospital in Dublin, Ireland.ParticipantsWe invited symptomatic and asymptomatic healthcare workers employed at the Rotunda Maternity Hospital to participate in the CAST study.Main Outcome MeasuresThe CAST study aimed to examine incidence 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.ResultsBy July 2020, 398 molecular tests had been completed on symptomatic staff with clinical suspicion of SARS-CoV-2 infection. In this cohort, 14% (n=54/398) had SARS-CoV-2 RNA detected by RT-PCR. The CAST study enrolled 137 HCWs with 86 participants symptomatic at time of swab collection and a further 51 asymptomatic control participants. SARS-CoV-2 RNA was detected in 52% (n=45/86) symptomatic study participants and serological positivity was confirmed in 98% (n=44/45) of those participants. Asymptomatic SARS-CoV-2 RNA infection was detected in 4% (n=2/51) of control participants with a seropositivity rate in this group of 8% (n=4/51). We demonstrated that 95% of SARS-CoV-2 PCR 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 a healthcare setting, as the ongoing pandemic continues.FundingThe CAST study was supported by the Rotunda Hospital and Trinity Biotech.