Data from: Detection of silent SARS-CoV-2 infection (S1 File)

Background: To control COVID-19 pandemic is of critical importance to the
global public health. To capture the prevalence in an accurate and timely
manner and to understand the mode of nosocomial infection are essential
for its preventive measure. Methods: We recruited 685 healthcare workers
(HCW’s) at Tokyo Shinagawa Hospital prior to the vaccination with COVID-19
vaccine. Sera of the subjects were tested by assays for the titer of IgG
against S protein’s receptor binding domain (IgG (RBD)) or IgG against
nucleocapsid protein (IgG (N)) of SARS-CoV-2. Together with PCR data, the
positive rates by these methods were evaluated. Results: Overall positive
rates among HCW’s by PCR, IgG (RBD), IgG (N) with a cut-off of 1.4 S/C
(IgG (N)1.4), and IgG (N) with a cut-off of 0.2 S/C (IgG (N)0.2) were
3.5%, 9.5%, 6.1%, and 27.7%, respectively. Positive rates of HCW’s working
in COVID-19 ward were significantly higher than those of HCW’s working in
non-COVID-19 ward by all the four methods. Concordances of IgG (RBD), IgG
(N)1.4, and IgG (N)0.2 against PCR were 97.1%, 71.4%, and 88.6%,
respectively. By subtracting the positive rates of PCR from that of IgG
(RBD), the rate of overall silent infection and that of HCW’s in COVID-19
ward were estimated to be 6.0% and 21.1%, respectively.
Conclusions:  For the prevention of nosocomial infection of
SARS-CoV-2, identification of silent infection is essential. For the
detection of ongoing infection, periodical screening with IgG (RBD) in
addition to PCR would be an effective measure. For the surveillance of
morbidity in the population, on the other hand, IgG (N)0.2 could be the
most reliable indicator among the three serological tests.