The prevalence of severe acute respiratory coronavirus virus 2 (SARS-CoV-2) IgG antibodies in intensive care unit (ICU) healthcare personnel (HCP) and its implications—a single-center, prospective, pilot study

To the Editor—Healthcare personnel (HCP), including practitioners, nursing staff, respiratory therapists, and the pronepositioning team caring for coronavirus disease 2019 (COVID-19) patients in the intensive care unit (ICU) are considered to have a high risk of exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Most patients admitted to the ICU are severely sick and need to be intubated. High-risk procedures for droplet dispersion, including tracheal intubation and tracheostomy tube placement, can be performed in the ICU.1 In a community seroprevalence study in Los Angeles County, the prevalence of antibodies to SARS-CoV-2 was 4.65%.2 To our knowledge, no other study has addressed the prevalence of subclinical seroconversion of SARSCoV-2 among HCP in the ICU setting. In this study, we investigated the seroconversion of asymptomatic SARS-CoV-2 infection in ICU HCP exposed to critically ill COVID-19 patients.

To the Editor-Healthcare personnel (HCP), including practitioners, nursing staff, respiratory therapists, and the pronepositioning team caring for coronavirus disease 2019 (COVID-19) patients in the intensive care unit (ICU) are considered to have a high risk of exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Most patients admitted to the ICU are severely sick and need to be intubated. High-risk procedures for droplet dispersion, including tracheal intubation and tracheostomy tube placement, can be performed in the ICU. 1 In a community seroprevalence study in Los Angeles County, the prevalence of antibodies to SARS-CoV-2 was 4.65%. 2 To our knowledge, no other study has addressed the prevalence of subclinical seroconversion of SARS-CoV-2 among HCP in the ICU setting. In this study, we investigated the seroconversion of asymptomatic SARS-CoV-2 infection in ICU HCP exposed to critically ill COVID-19 patients.

Methods
This single-center, prospective, pilot study was performed in an ICU at a teaching hospital, Monmouth Medical Center in Long Branch, New Jersey. It was approved by our institutional review board. All HCP caring for COVID-19 patients in the ICU setting from March 1, 2020, to April 30, 2020, were eligible for inclusion in the study. A cross-sectional survey questionnaire was utilized to collect demographic characteristics and to exclude HCP who (1) tested positive for SARS-CoV-2 by reverse transcriptasepolymerase chain reaction assay (RT-PCR), (2) had symptoms consistent with COVID-19, or (3) had COVID-19 exposure in a household setting. In total, 134 ICU HCP responded to the survey, and 121 HCP were eligible for SARS-CoV-2-specific IgG antibody testing. Means and interquartile ranges (IQRs) were used for continuous variables. All participants provided written consent. Antibody testing was performed on the sera using a rapid immunochromatography test (STANDARD Q COVID-19 IgM/IgG Duo, SD Biosensor, Suwon-si, Korea) by lateral flow in a Clinical Laboratory Improvement Amendments certified (CLIA), high-complexity laboratory. The manufacturer's stated sensitivity and specificity for IgG, 15-21 days after symptoms onset are 96.2% and 96.6%, respectively. Blood specimens were drawn from 2 weeks after the specified period commencing May 14, 2020, and ending May 19, 2020.

Results
Overall, 134 ICU HCP responded to the survey: 75% were women, 47.73% were registered nurses, 9.85% were attending physicians, 26.52% were resident physicians, 6.82% were patient care assistants, 6.82% were respiratory therapists, 1.52% were technicians, and 0.76% were anesthetists. The mean age of the respondents was 39.2 years (IQR, 28-48.5). The mean duration of work was 29.3 days (IQR, 16.0-40.0). Of 134 ICU HCP eligible staff, 13 were excluded and 121 underwent SARS-CoV-2-specific IgG antibody testing. One individual tested positive and 1 test result was inconclusive due to a faulty test kit and was removed from the analysis. In this study, the prevalence of asymptomatic seroconversion was 0.83%.

Discussion
Information about the prevalence of asymptomatic seroconversion of SARS-CoV-2 in HCP is limited. In a preliminary report released by the Centers for Disease Control and Prevention (CDC), nearly 9,282 HCP have contracted COVID-19, and 27 have died. 3 Okba et al 4 demonstrated that most PCR-confirmed SARS-CoV-2 patients seroconverted after 2 weeks of disease onset. 4 Our study revealed a prevalence of 0.83%, which indicates that seroconversion in ICU HCP was a rare event. These data indicate that proper education and utilization of personal protective equipment (PPE) is effective. 5 Additionally, ventilated patients have less aerosolization and were housed in a negative-pressure environment in the ICU isolation rooms, which also may have been factors in avoiding transmission to HCP.
Our study has several limitations. It was conducted in a single-center ICU and did not include long-term clinical or laboratory follow-up. Studies with larger sample sizes in different healthcare settings would be useful to validate the clinical impact of our findings.