Seroprevalence of SARS-CoV-2 antibodies among healthcare workers in Dutch hospitals after the 2020 first wave: a multicentre cross-sectional study with prospective follow-up
Authors: Recanatini Claudia , GeurtsvanKessel Corine H. , Pas Suzan D. , Broens Els M. , Maas Martje , van Mansfeld Rosa , Mutsaers-van Oudheusden Anne J. G. , van Rijen Miranda , Schippers Emile F. , Stegeman Arjan , Tami Adriana , Veldkamp Karin Ellen , Visser Hannah , Voss Andreas , Wegdam-Blans Marjolijn C. A. , Wertheim Heiman F. L. , Wever Peter C. , Koopmans Marion P. G. , Kluytmans Jan A. J. W. , Kluytmans-van den Bergh Marjolein F. Q. ,   COCON Study Group, Bergmans Anneke , van den Bijllaardt Wouter , Broens Els , Buiting Anton , Dohmen Wietske , Friedrich Alexander , GeurtsvanKessel Corine , van der Gun Bernardina , Heederik Dick , de Jong Menno , Kluytmans Jan , Kluytmans-van den Bergh Marjolein , Koopmans Marion , Maas Martje , van Mansfeld Rosa , Meijer Angelique , Murk Jean-Luc , Nabuurs Marrigje , Niesters Bert , ten Oever Jaap , Mutsaers-van Oudheusden Anne , Pas Suzan , Recanatini Claudia , van Rijen Miranda , Schippers Emile , Schweitzer Valentijn , Stegeman Arjan , Streefkerk Roel , Tami Adriana , Veldkamp Karin Ellen , Veloo Alida , Visser Hannah , Voss Andreas , de Vries Jutte , Wegdam-Blans Marjolijn , Wertheim Heiman , Wever Peter , Wold Karin , Wunderink Herman 
Published: November 2023

Abstract
Background
We aimed to estimate the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroprevalence and describe its determinants and associated symptoms among unvaccinated healthcare workers (HCWs) after the first wave of the pandemic.

Methods
HCWs from 13 Dutch hospitals were screened for antibodies against the spike protein of SARS-CoV-2 in June-July 2020 and after three months. Participants completed a retrospective questionnaire on determinants for occupational and community exposure to SARS-CoV-2 and symptoms suggestive of COVID-19 experienced since January 2020. The seroprevalence was calculated per baseline characteristic and symptom at baseline and after follow-up. Adjusted odds ratios (aOR) for seropositivity were determined using logistic regression.

Results
Among 2328 HCWs, 323 (13.9%) were seropositive at enrolment, 49 of whom (15%) reported no previous symptoms suggestive of COVID-19. During follow-up, only 1% of the tested participants seroconverted. Seroprevalence was higher in younger HCWs compared to the mid-age category (aOR 1.53, 95% CI 1.07–2.18). Nurses (aOR 2.21, 95% CI 1.34–3.64) and administrative staff (aOR 1.87, 95% CI 1.02–3.43) had a higher seroprevalence than physicians. The highest seroprevalence was observed in HCWs in the emergency department (ED) (aOR 1.79, 95% CI 1.10–2.91), the lowest in HCWs in the intensive, high, or medium care units (aOR 0.47, 95% CI 0.31–0.71). Chronic respiratory disease, smoking, and having a dog were independently associated with a lower seroprevalence, while HCWs with diabetes mellitus had a higher seroprevalence. In a multivariable model containing all self-reported symptoms since January 2020, altered smell and taste, fever, general malaise/fatigue, and muscle aches were positively associated with developing antibodies, while sore throat and chills were negatively associated.

Conclusions
The SARS-CoV-2 seroprevalence in unvaccinated HCWs of 13 Dutch hospitals was 14% in June-July 2020 and remained stable after three months. A higher seroprevalence was observed in the ED and among nurses, administrative and young staff, and those with diabetes mellitus, while a lower seroprevalence was found in HCWs in intensive, high, or medium care, and those with self-reported lung disease, smokers, and dog owners. A history of altered smell or taste, fever, muscle aches and fatigue were independently associated with the presence of SARS-CoV-2 antibodies in unvaccinated HCWs.