Seroprevalence of antibodies against SARS-CoV-2 among health care workers in a large Spanish reference hospital

Abstract

Background: Health care workers (HCW) are a high-risk population to acquire SARS-CoV-2 infection from patients or other fellow HCW. At the same time, they can be contagious to highly vulnerable individuals seeking health care. This study aims at estimating the seroprevalence of antibodies against SARS-CoV-2 and associated factors in HCW from a large referral hospital in Barcelona, Spain, one of the countries hardest hit by COVID-19 in the world. Methods: From 28 March to 9 April 2020, we recruited a random sample of 578 HCW from the human resources database of Hospital Clinic in Barcelona. We collected a nasopharyngeal swab for direct SARS-CoV-2 detection through real time reverse-transcriptase polymerase chain reaction (rRT-PCR), as well as blood for plasma antibody quantification. IgM, IgG and IgA antibodies to the receptor-binding domain of the spike protein were measured by Luminex. The cumulative prevalence of infection (past or current) was defined by a positive SARS-CoV-2 rRT-PCR and/or antibody seropositivity. Results: Of the 578 total participants, 39 (6.7%, 95% CI: 4.8-9.1) had been previously diagnosed with COVID-19 by rRT-PCR, 14 (2.4%, 95% CI: 1.4-4.3) had a positive rRT-PCR at recruitment, and 54 (9.3%, 95% CI: 7.2-12.0) were seropositive for IgM and/or IgG and/or IgA against SARS-CoV-2. Of the 54 seropositive HCW, 21 (38.9%) had not been previously diagnosed with COVID-19, although 10 of them (47.6%) reported past COVID-19-compatible symptoms. The cumulative prevalence of SARS-CoV-2 infection was 11.2% (65/578, 95% CI: 8.9-14.1). Among those with evidence of past or current infection, 40.0% (26/65) had not been previously diagnosed with COVID-19, of which 46.2% (12/26) had history of COVID-19-compatible symptoms. The odds of being seropositive was higher in participants who reported any COVID-19 symptom (OR: 8.84, 95% CI: 4.41-17.73). IgM levels positively correlated with age (rho=0.36, p-value=0.031) and were higher in participants with more than 10 days since onset of symptoms (p-value=0.022), and IgA levels were higher in symptomatic than asymptomatic subjects (p-value=0.041). Conclusions: The seroprevalence of antibodies against SARS-CoV-2 among HCW was lower than expected. Thus, being a high-risk population, we anticipate these estimates to be an upper limit to the seroprevalence of the general population. Forty per cent of those with past or present infection had not been previously diagnosed with COVID-19, which calls for active periodic rRT-PCR testing among all HCW to minimize potential risk of hospital-acquired SARS-CoV-2 infections.

Antibody response to SARS-CoV-2 infection in humans: a systematic review

“…• Four studies report no association between antibody titres (either IgG or IgM) and sex. 21,148,163,164 • Two studies report a higher IgG titre in women, 165,166 although one found this association in severe patients only. 166…”

“…Three studies reported that older people had higher titres of IgA and IgG, 23 IgM, 163 and anti-S and anti-RBD IgG. 160…”

“SARS-CoV-2 antibody seroprevalence and stability in a tertiary care hospital-setting”

“…However, it is important to assess the stability of the antibodies to estimate for how long an individual might be protected from re-infection. Several studies have been conducted to look at the seroprevalence of antibodies against SARS-CoV-2 in different parts of the world [7][8][9][10][11][12] . They have reported the presence of antibodies among the asymptomatic individuals along with confirmed COVID-19 cases.…”

Peer Review #1 of "Collaborative networks enable the rapid establishment of serological assays for SARS-CoV-2 during nationwide lockdown in New Zealand (v0.1)"

“…Numerous laboratory-based serological assays for SARS-CoV-2 are being developed worldwide including enzyme-linked immunosorbent assays (ELISAs) and bead-based immunoassays for measurement of SARS-CoV-2 antibodies (Petherick, 2020;Garcia-Basteiro et al, 2020;, as well as virus neutralisation assays for quantification of neutralising antibodies (Tan et al, 2020;Anderson et al, 2020). The spike protein (S protein) expressed by SARS-CoV-2 contains a receptor binding domain (RBD), which interacts with host cells via the human angiotensin-converting enzyme 2 (hACE2) (Diamond & Pierson, 2020).…”

“…The spike protein (S protein) expressed by SARS-CoV-2 contains a receptor binding domain (RBD), which interacts with host cells via the human angiotensin-converting enzyme 2 (hACE2) (Diamond & Pierson, 2020). The S protein is highly immunogenic and, given the integral role of the S protein and RBD in facilitating viral entry, these antigens form the basis of many immunoassays described to date (Duan et al, 2020;Garcia-Basteiro et al, 2020;Long et al, 2020;Amanat et al, 2020). Recent data from immunoassays based on the SARS-CoV-2 nucleocapsid protein also show high sensitivity (Sethuraman, Jeremiah & Ryo, 2020;Bryan et al, 2020).…”