Prevalence and incidence of anti-SARS-CoV-2 antibodies among healthcare workers in Belgian hospitals before vaccination: a prospective cohort study

Laure Mortgat; Kristien Verdonck; Veronik Hutse; Isabelle Thomas; Cyril Barbezange; Leo Heyndrickx; Natalie Fischer; Bea Vuylsteke; Ines Kabouche; Kevin K Ariën; Isabelle Desombere; Els Duysburgh

doi:10.1136/bmjopen-2021-050824

Prevalence and incidence of anti-SARS-CoV-2 antibodies among healthcare workers in Belgian hospitals before vaccination: a prospective cohort study

Laure Mortgat, Kristien Verdonck, Veronik Hutse, Isabelle Thomas, Cyril Barbezange, Leo Heyndrickx, Natalie Fischer, Bea Vuylsteke, Ines Kabouche, Kevin K Ariën, Isabelle Desombere, Els Duysburgh

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Abstract

OBJECTIVES: To describe prevalence and incidence of anti-SARS-CoV-2 antibodies among Belgian hospital healthcare workers (HCW) in April-December 2020.

DESIGN: Prospective cohort study. Follow-up was originally planned until September and later extended.

SETTING: Multicentre study, 17 hospitals.

PARTICIPANTS: 50 HCW were randomly selected per hospital. HCW employed beyond the end of the study and whose profession involved contact with patients were eligible. 850 HCW entered the study in April-May 2020, 673 HCW (79%) attended the September visit and 308 (36%) the December visit.

OUTCOME MEASURES: A semiquantitative ELISA was used to detect IgG against SARS-CoV-2 in serum (Euroimmun) at 10 time points. In seropositive samples, neutralising antibodies were measured using a virus neutralisation test. Real-time reverse transcription PCR (RT-qPCR) was performed to detect SARS-CoV-2 on nasopharyngeal swabs. Participant characteristics and the presence of symptoms were collected via an online questionnaire.

RESULTS: Among all participants, 80% were women, 60% nurses and 21% physicians. Median age was 40 years. The seroprevalence remained relatively stable from April (7.7% (95% CI: 4.8% to 12.1%) to September (8.2% (95% CI: 5.7% to 11.6%)) and increased thereafter, reaching 19.7% (95% CI: 12.0% to 30.6%) in December 2020. 76 of 778 initially seronegative participants seroconverted during the follow-up (incidence: 205/1000 person-years). Among all seropositive individuals, 118/148 (80%) had a positive neutralisation test, 83/147 (56%) presented or reported a positive RT-qPCR, and 130/147 (88%) reported COVID-19-compatible symptoms at least once. However, only 46/73 (63%) of the seroconverters presented COVID-19-compatible symptoms in the month prior to seroconversion.

CONCLUSIONS: The seroprevalence among hospital HCW was slightly higher than that of the general Belgian population but followed a similar evolution, suggesting that infection prevention and control measures were effective and should be strictly maintained. After two SARS-CoV-2 waves, 80% of HCW remained seronegative, justifying their prioritisation in the vaccination strategy.

TRIAL REGISTRATION NUMBER: NCT04373889.

Original language	English
Article number	e050824
Journal	BMJ Open
Volume	11
Issue number	6
Number of pages	10
ISSN	2044-6055
DOIs	https://doi.org/10.1136/bmjopen-2021-050824
Publication status	Published - 2021

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Mortgat, L., Verdonck, K., Hutse, V., Thomas, I., Barbezange, C., Heyndrickx, L., Fischer, N., Vuylsteke, B., Kabouche, I., Ariën, K. K., Desombere, I., & Duysburgh, E. (2021). Prevalence and incidence of anti-SARS-CoV-2 antibodies among healthcare workers in Belgian hospitals before vaccination: a prospective cohort study. BMJ Open, 11(6), Article e050824. https://doi.org/10.1136/bmjopen-2021-050824

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title = "Prevalence and incidence of anti-SARS-CoV-2 antibodies among healthcare workers in Belgian hospitals before vaccination: a prospective cohort study",

abstract = "OBJECTIVES: To describe prevalence and incidence of anti-SARS-CoV-2 antibodies among Belgian hospital healthcare workers (HCW) in April-December 2020.DESIGN: Prospective cohort study. Follow-up was originally planned until September and later extended.SETTING: Multicentre study, 17 hospitals.PARTICIPANTS: 50 HCW were randomly selected per hospital. HCW employed beyond the end of the study and whose profession involved contact with patients were eligible. 850 HCW entered the study in April-May 2020, 673 HCW (79%) attended the September visit and 308 (36%) the December visit.OUTCOME MEASURES: A semiquantitative ELISA was used to detect IgG against SARS-CoV-2 in serum (Euroimmun) at 10 time points. In seropositive samples, neutralising antibodies were measured using a virus neutralisation test. Real-time reverse transcription PCR (RT-qPCR) was performed to detect SARS-CoV-2 on nasopharyngeal swabs. Participant characteristics and the presence of symptoms were collected via an online questionnaire.RESULTS: Among all participants, 80% were women, 60% nurses and 21% physicians. Median age was 40 years. The seroprevalence remained relatively stable from April (7.7% (95% CI: 4.8% to 12.1%) to September (8.2% (95% CI: 5.7% to 11.6%)) and increased thereafter, reaching 19.7% (95% CI: 12.0% to 30.6%) in December 2020. 76 of 778 initially seronegative participants seroconverted during the follow-up (incidence: 205/1000 person-years). Among all seropositive individuals, 118/148 (80%) had a positive neutralisation test, 83/147 (56%) presented or reported a positive RT-qPCR, and 130/147 (88%) reported COVID-19-compatible symptoms at least once. However, only 46/73 (63%) of the seroconverters presented COVID-19-compatible symptoms in the month prior to seroconversion.CONCLUSIONS: The seroprevalence among hospital HCW was slightly higher than that of the general Belgian population but followed a similar evolution, suggesting that infection prevention and control measures were effective and should be strictly maintained. After two SARS-CoV-2 waves, 80% of HCW remained seronegative, justifying their prioritisation in the vaccination strategy.TRIAL REGISTRATION NUMBER: NCT04373889.",

author = "Laure Mortgat and Kristien Verdonck and Veronik Hutse and Isabelle Thomas and Cyril Barbezange and Leo Heyndrickx and Natalie Fischer and Bea Vuylsteke and Ines Kabouche and Ari{\"e}n, {Kevin K} and Isabelle Desombere and Els Duysburgh",

note = "FTX; DOAJ; (CC BY-NC 4.0); {\textcopyright} Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.",

year = "2021",

doi = "10.1136/bmjopen-2021-050824",

language = "English",

volume = "11",

journal = "BMJ Open",

issn = "2044-6055",

publisher = "BMJ Publishing Group",

number = "6",

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Mortgat, L, Verdonck, K, Hutse, V, Thomas, I, Barbezange, C, Heyndrickx, L, Fischer, N, Vuylsteke, B, Kabouche, I, Ariën, KK, Desombere, I & Duysburgh, E 2021, 'Prevalence and incidence of anti-SARS-CoV-2 antibodies among healthcare workers in Belgian hospitals before vaccination: a prospective cohort study', BMJ Open, vol. 11, no. 6, e050824. https://doi.org/10.1136/bmjopen-2021-050824

TY - JOUR

T1 - Prevalence and incidence of anti-SARS-CoV-2 antibodies among healthcare workers in Belgian hospitals before vaccination: a prospective cohort study

AU - Mortgat, Laure

AU - Verdonck, Kristien

AU - Hutse, Veronik

AU - Thomas, Isabelle

AU - Barbezange, Cyril

AU - Heyndrickx, Leo

AU - Fischer, Natalie

AU - Vuylsteke, Bea

AU - Kabouche, Ines

AU - Ariën, Kevin K

AU - Desombere, Isabelle

AU - Duysburgh, Els

PY - 2021

Y1 - 2021

N2 - OBJECTIVES: To describe prevalence and incidence of anti-SARS-CoV-2 antibodies among Belgian hospital healthcare workers (HCW) in April-December 2020.DESIGN: Prospective cohort study. Follow-up was originally planned until September and later extended.SETTING: Multicentre study, 17 hospitals.PARTICIPANTS: 50 HCW were randomly selected per hospital. HCW employed beyond the end of the study and whose profession involved contact with patients were eligible. 850 HCW entered the study in April-May 2020, 673 HCW (79%) attended the September visit and 308 (36%) the December visit.OUTCOME MEASURES: A semiquantitative ELISA was used to detect IgG against SARS-CoV-2 in serum (Euroimmun) at 10 time points. In seropositive samples, neutralising antibodies were measured using a virus neutralisation test. Real-time reverse transcription PCR (RT-qPCR) was performed to detect SARS-CoV-2 on nasopharyngeal swabs. Participant characteristics and the presence of symptoms were collected via an online questionnaire.RESULTS: Among all participants, 80% were women, 60% nurses and 21% physicians. Median age was 40 years. The seroprevalence remained relatively stable from April (7.7% (95% CI: 4.8% to 12.1%) to September (8.2% (95% CI: 5.7% to 11.6%)) and increased thereafter, reaching 19.7% (95% CI: 12.0% to 30.6%) in December 2020. 76 of 778 initially seronegative participants seroconverted during the follow-up (incidence: 205/1000 person-years). Among all seropositive individuals, 118/148 (80%) had a positive neutralisation test, 83/147 (56%) presented or reported a positive RT-qPCR, and 130/147 (88%) reported COVID-19-compatible symptoms at least once. However, only 46/73 (63%) of the seroconverters presented COVID-19-compatible symptoms in the month prior to seroconversion.CONCLUSIONS: The seroprevalence among hospital HCW was slightly higher than that of the general Belgian population but followed a similar evolution, suggesting that infection prevention and control measures were effective and should be strictly maintained. After two SARS-CoV-2 waves, 80% of HCW remained seronegative, justifying their prioritisation in the vaccination strategy.TRIAL REGISTRATION NUMBER: NCT04373889.

AB - OBJECTIVES: To describe prevalence and incidence of anti-SARS-CoV-2 antibodies among Belgian hospital healthcare workers (HCW) in April-December 2020.DESIGN: Prospective cohort study. Follow-up was originally planned until September and later extended.SETTING: Multicentre study, 17 hospitals.PARTICIPANTS: 50 HCW were randomly selected per hospital. HCW employed beyond the end of the study and whose profession involved contact with patients were eligible. 850 HCW entered the study in April-May 2020, 673 HCW (79%) attended the September visit and 308 (36%) the December visit.OUTCOME MEASURES: A semiquantitative ELISA was used to detect IgG against SARS-CoV-2 in serum (Euroimmun) at 10 time points. In seropositive samples, neutralising antibodies were measured using a virus neutralisation test. Real-time reverse transcription PCR (RT-qPCR) was performed to detect SARS-CoV-2 on nasopharyngeal swabs. Participant characteristics and the presence of symptoms were collected via an online questionnaire.RESULTS: Among all participants, 80% were women, 60% nurses and 21% physicians. Median age was 40 years. The seroprevalence remained relatively stable from April (7.7% (95% CI: 4.8% to 12.1%) to September (8.2% (95% CI: 5.7% to 11.6%)) and increased thereafter, reaching 19.7% (95% CI: 12.0% to 30.6%) in December 2020. 76 of 778 initially seronegative participants seroconverted during the follow-up (incidence: 205/1000 person-years). Among all seropositive individuals, 118/148 (80%) had a positive neutralisation test, 83/147 (56%) presented or reported a positive RT-qPCR, and 130/147 (88%) reported COVID-19-compatible symptoms at least once. However, only 46/73 (63%) of the seroconverters presented COVID-19-compatible symptoms in the month prior to seroconversion.CONCLUSIONS: The seroprevalence among hospital HCW was slightly higher than that of the general Belgian population but followed a similar evolution, suggesting that infection prevention and control measures were effective and should be strictly maintained. After two SARS-CoV-2 waves, 80% of HCW remained seronegative, justifying their prioritisation in the vaccination strategy.TRIAL REGISTRATION NUMBER: NCT04373889.

U2 - 10.1136/bmjopen-2021-050824

DO - 10.1136/bmjopen-2021-050824

M3 - A1: Web of Science-article

C2 - 34187832

SN - 2044-6055

VL - 11

JO - BMJ Open

JF - BMJ Open

IS - 6

M1 - e050824

ER -

Prevalence and incidence of anti-SARS-CoV-2 antibodies among healthcare workers in Belgian hospitals before vaccination: a prospective cohort study

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