1
Prevalence of IgG antibodies against SARS-CoV-2 among healthcare workers in a tertiary pediatric
1
hospital in Poland 2
3
Beata Kasztelewicz
1*
, Katarzyna Janiszewska
1
, Julia Burzy
ń
ska
1
, Emilia Szydłowska
1
, Marek Migdał
2
, 4
Katarzyna Dzier
ż
anowska-Fangrat
1
5
6
1
Department of Clinical Microbiology and Immunology, The Children’s Memorial Health Institute, Warsaw, 7
Poland 8
2
Department of Anaesthesiology and Intensive Care, The Children’s Memorial Health Institute, Warsaw, Poland 9
10
11
12
*Corresponding author 13
b.kasztelewicz@ipczd.pl (BK) 14
15
. CC-BY-NC-ND 4.0 International licenseIt is made available under a
is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.(which was not certified by peer review)preprint
The copyright holder for thisthis version posted November 30, 2020. ; https://doi.org/10.1101/2020.11.28.20239848doi: medRxiv preprint
NOTE: This preprint reports new research that has not been certified by peer review and should not be used to guide clinical practice.
2
Abstract 16
Data on prevalence of SARS-CoV-2 antibody in healthcare workers (HCWs) is scare, especially in pediatric 17
settings. The purpose of this study was to evaluate the SARS-CoV-2 IgG-positivity among HCWs of a tertiary 18
pediatric hospital. In addition, follow-up of serological response in the subgroup of seropositive HCWs was 19
performed, to get some insight on persistence of IgG antibodies to SARS-CoV-2. Free, voluntary SARS-CoV-2 20
IgG testing was made available to HCWs of the Children’s Memorial Health Institute in Warsaw (Poland). 21
Plasma samples were collected between July 1 and August 9, 2020 and tested using the Abbott SARS-CoV-2 22
IgG assay. Of 2282 eligible participants, 1879 (82.3%) HCWs volunteered to undergo testing. Sixteen HCWs 23
tested positive for SARS-CoV-2 IgG, corresponding to the seroprevalence of 0.85%. Among seropositive 24
HCWs, three had confirmed COVID-19. Of note, 8 (50%) seropositive HCWs reported neither symptoms nor 25
unprotected contact with confirmed SARS-CoV-2 cases in the previous months. A decline in the IgG index was 26
observed at median time of 86.5 days (range:84-128 days) after symptom onset or RT-PCR testing. The 27
nationwide public health response measures together with infection prevention and control practices 28
implemented at the hospital level, at the beginning of the COVID-19 pandemic, might explain a low 29
seroprevalence. Further studies are warranted to elucidate the duration of anti-SARS-CoV-2 antibodies, as well 30
as the correlation between seropositivity and protective immunity against reinfection. Regardless of the 31
persistence of antibodies and their protective properties, such low prevalence indicates that this population is 32
vulnerable to a second wave of the COVID-19 pandemic. 33
34
. CC-BY-NC-ND 4.0 International licenseIt is made available under a
is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.(which was not certified by peer review)preprint
The copyright holder for thisthis version posted November 30, 2020. ; https://doi.org/10.1101/2020.11.28.20239848doi: medRxiv preprint
3
Introduction 35
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), causing coronavirus disease 2019 (COVID-36
19) which emerged in December 2019, has evolved to a global pandemic [1]. In Poland first, imported COVID-37
19 case was reported on March, 3 2020 and 3 weeks later a nationwide lockdown was commenced [2]. Until 38
August, 31, there were 66 870 confirmed cases, with 2 033 COVID-19 related deaths [3]. 39
In the Masovian district (one of the three most affected regions in Poland) the first cases were recorded on 40
March 13 and by the end of August 2020, there were 9370 cases and 411 deaths [4]. 41
Although real-time RT-PCR is considered the gold standard for the diagnosis of the acute SARS-CoV-2 42
infection, this test is limited by transient nature of RNA. In addition, the sensitivity of RT-PCR methods is 43
estimated to be no higher than 70% [5], which may lead to underdiagnosing of SARS-CoV-2 infections, 44
especially in subclinical or asymptomatic cases. By identifying individuals who have developed antibodies to the 45
virus (including those that may be asymptomatic or have recovered), serology can give greater details into the 46
prevalence of SARS-CoV-2. Although, concerns have arisen on persistence of IgG antibodies to SARS-CoV-2 47
after recovery [6,7]. 48
Two entitles of infected individuals pose the highest risk for SARS-CoV-2 transmission in the hospital setting. 49
First, infected patients until diagnosis. Second, SARS-CoV-2-positive health care workers (HCWs). As children 50
and adolescent comprise less than 5% of all positive cases in Europe [8], majority of SARS-CoV-2 infections 51
among HCWs in pediatric hospitals might be associated with transmission in community or from infected co-52
workers. 53
Data on SARS-CoV-2 prevalence among HCWs in pediatric hospital settings is scare [9,10]. 54
Knowing the prevalence of SARS-CoV-2 infection among HCWs is vital to inform pandemic response. The aim 55
of this study was to evaluate the SARS-CoV-2 IgG positivity among HCWs of a tertiary pediatric hospital in 56
Warsaw (Masovian district), Poland. In addition, we have performed follow-up of serological response to SARS-57
CoV-2 in the subgroup of seropositive HCWs, to get some insight on persistence of specific antibodies. 58
59
Materials and methods 60
Free, voluntary SARS-CoV-2 IgG testing was made available to the hospital staff of the Children’s Memorial 61
Health Institute (CMHI) in Warsaw, Poland (including physicians, nurses, other workers with direct patient 62
contact, i.e. physical therapists as well as workers without direct patient contact, i.e. laboratory workers, 63
. CC-BY-NC-ND 4.0 International licenseIt is made available under a
is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.(which was not certified by peer review)preprint
The copyright holder for thisthis version posted November 30, 2020. ; https://doi.org/10.1101/2020.11.28.20239848doi: medRxiv preprint
4
pharmacists, administrative staff, maintenance, etc.). All participants were asymptomatic at the time of serology
64
testing. In particular, those who were previously symptomatic, had no symptoms for at least 14 days. Plasma 65
(EDTA) samples were collected between July 1 and August 9, 2020 (corresponding to 97 – 135 days after the 66
nation-wide lockdown was commenced). 67
Plasma samples were run on the Abbott Alinity i instrument using the Abbott SARS-CoV-2 IgG assay (Abbott 68
Laboratories, Lake Bluff, IL, USA) following manufacturer’s instruction. The assay is a chemiluminescent 69
microparticle immunoassay (CMIA) for qualitative detection of IgG antibodies to the nucleocapsid (N) protein 70
of SARS-CoV-2. The manufacturer’s index value (a signal/cut-off; S/CO ratio) of
≥
1.40 was interpreted as 71
positive. The assay has been shown to have 99.9% specificity and 100% sensitivity for samples taken greater 72
than 17 days post symptom onset [11]. 73
Demographic data (age, gender), results of SARS-CoV-2 RNA testing (if performed in CMHI) were collected 74
for all participants, from the laboratory records. Data on profession and the necessity of quarantine or isolation 75
(date and duration of quarantine or isolation) were collected from human resource’s database. In addition, 76
seropositive or previously SARS-CoV-2 infected individuals were approached telephonically and data regarding 77
contacts with a confirmed or suspected COVID-19 case, the positive test result in the past (if performed outside 78
CMHI), the necessity of inpatient treatment, experienced symptoms over the previous months, were collected by 79
the head of the infection control department. All data were analyzed anonymously. 80
81
Study setting 82
The CMHI in Warsaw (Masovian district), is the largest tertiary pediatric hospital and research institute in 83
Poland. With over 590 beds and 2282 employees it performs over 249 000 services (including inpatients and 84
outpatients) per year. 85
At the time of serology testing, we had no case of SARS-CoV-2 infection among patients. Until July1, 2020, the 86
first day of the serology testing, we had had 5 confirmed SARS-CoV-2 infections among HCWs (all contracted 87
outside the hospital setting, one confirmed outside CMHI) and there were no additional cases until July 6, 2020. 88
Since that time until August 9, 2020 (i.e. the end of the serology testing), additional 4 linked cases among 89
laboratory staff, were confirmed by RT-PCR (Fig 1). 90
91
Figure 1. The epidemic curve is shown as the number of HCWs tested each week for SARS-CoV-2 RNA by 92
RT-PCR in CMHI together with the number of new SARS-CoV-2 cases recorded in the Masovian district. The 93
. CC-BY-NC-ND 4.0 International licenseIt is made available under a
is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.(which was not certified by peer review)preprint
The copyright holder for thisthis version posted November 30, 2020. ; https://doi.org/10.1101/2020.11.28.20239848doi: medRxiv preprint
5
first case of SARS-CoV-2 RNA among HCWs of CMHI was detected on March, 17 2020. Voluntary serological
94
testing for HCWs of CMHI was conducted from July 1 to August 9, 2020 (corresponding to week 27 and 32). 95
Details of infection prevention and control measures implemented at CMHI together with the nationwide 96
lockdown, are given below the curve. 97
98
Statistical analysis 99
Statistical analysis was carried out using the Statistica data analysis software system (TIBCO Software Inc.), 100
version 13. Continuous variables were presented as median and interquartile range (IQR). Categorical variables 101
were summarized using percentages and counts. Seroprevalence of SARS-CoV-2 IgG was calculated as 102
proportion with 95% confidence intervals (CI). The association between variables was tested with Chi-square or 103
Fisher’s exact test (for categorical variables) and Mann Whitney U test (for continuous variables). Univariable 104
and multivariable logistic regression analysis were run to evaluate factors associated with seroprevalence of 105
SARS-CoV-2 IgG. For the variables to be included in multiple logistic model, a stepwise selection was used, 106
starting with the full model, and using p-value of 0.1 for removal and 0.05 for addition of variables. 107
108
Ethical consideration 109
This study reporting the results of free-voluntary serology testing, was not offered as a research protocol but as a 110
service to healthcare workers. The study has been reviewed and approved by the Institutional Review Board of 111
the Children’s Memorial Health Institute in Warsaw (Ref. no. 10/P-IN/20), and granted a waiver of consent since 112
the data were analyzed anonymously. 113
114
Results 115
Baseline characteristics 116
Of 2282 eligible participants, 1879 HCWs volunteered to undergo testing, yielding a participation rate of 82.3%. 117
Median (IQR) age was 48 (38-56) years, and 85.8% were female. Approximately one third (639/1879, 34%) 118
were nurses, and 19.7% were physicians. 119
Majority (70.9%) of HCWs worked in the clinical area. Twenty-two per cent (417/1879) had been tested for 120
SARS-CoV-2 RNA by RT-PCR as a part of implemented infection control measurements (note that 121
. CC-BY-NC-ND 4.0 International licenseIt is made available under a
is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.(which was not certified by peer review)preprint
The copyright holder for thisthis version posted November 30, 2020. ; https://doi.org/10.1101/2020.11.28.20239848doi: medRxiv preprint
