Screening of Health-care Workers in an University Hospital for SARS-CoV-2

The study protocol provides for a collection of basic data relating to all hospital workers
who voluntarily underwent the test (age, sex, type of occupation - doctor / nurse /
socio-health / administrative operator; attendance in Covid-19 wards department), IgG outcome
(quantitative level) and swab outcome (negative, weakly positive, positive).

The cohort of hospital workers constitutes a population of particular relevance for the
development of appropriate strategies for the surveillance of hospital risk for SARS-CoV-2
infection (relationship to the type of job, clinical evolution) and the available data are
very limited.

The asymptomatic staff cohort constitutes the ideal population context to contribute to
knowledge of aspects of the spread of the virus.

The limitations of current serological tests are well known, which do not allow to
distinguish the acute phase of the infection and therefore the persistence of contagiousness.
Similarly, the genomic characteristics of the SARS-CoV-2 virus are not known in asymptomatic
but swab positive subjects compared to the virus isolated from symptomatic patients.

In the cohort of operators who tested positive for nasopharyngeal swab (both symptomatic and
asymptomatic), the availability of serological tests will allow to evaluate the antibody
response over time in relation to the clinical evolution of the infection, and the
persistence of a protective titer over time.

Methods and study design

1. The cohort of symptomatic hospital workers who tested positive for the swab includes 250
operators. The cohort will be evaluated as a prospective epidemiological study;

2. The cohort of asymptomatic / paucisymptomatic operators will include the cohort of
operators who will test positive in the serological analysis. From the entire population
of hospital workers (over 3000), three controls will be identified for each operator who
tested positive for the serological test on the same day and are negative for the
serological test. Considering the positive percentage of 5.5% in the serological survey
(from the first epidemiological data reported at the ASST of Monza), the positive
screening cohort and the control cohort of about 480 are estimated at about 160.

3. The serological test that will be used is the one required by the indication of the
Circular G1.2020.00117959 of 22 April 2020. It is a test with the CLIA method designed
to recognize IgG antibodies directed against the S1 and S2 domains of the SARS virus
"spike" protein -CoV-2, selected for its ability to provide specificity for SARS-CoV-2
compared to other Coronaviruses.

The product has been designed to meet the need to identify in the population those who
have already been infected with the virus, whose diagnosis has not been made through the
execution of a swab and a molecular diagnostic test.

4. The questionnaire will be administered to all operators.

Data anonymization Health worker will be identified with an 8-digit code followed by the
letters OS and the year of collection (e.g. 00000001 OS / 2020); in biological sampling the
laboratory will identify the patient with the same code and that will be the linkage code
between the database and the bio-bank because it is unique for each worker at the ASST in
Monza.

Biological studies

The fields of research in the biological field that the protocol aims to pursue are listed
below:

1. Characterizing the SARS-CoV-2 genome in relation to the characteristics of the hospital
workers from which the virus is extracted and sequenced is relevant for knowing the
functional mechanisms of the virus in relation to the host - both for clinical and
diagnostic purposes, as well as for predict virus mutations and related clinical
response in view of a second SARS-CoV-2 epidemic;

2. Evaluate the relevance of tests with greater sensitivity and specificity in the
population negative for the throat swab but positive for the serological investigation;

3. Study of biomolecular markers of COVID-19 infection with the aim of identifying the
basis of the different susceptibility in relation to age, sex and the presence of
co-morbidities;

4. Evaluate metabolic biochemical markers of resistance to viral infection in a subgroup of
hospital workers with positive swab and in a subgroup with positive antibody test but
negative swab to be evaluated at the first available sample and after at least 3 months
to allow 27 hydroxycholesterol to return at the concentration prior to infection.

Statistic analysis Central tendency and dispersion measures will be used for descriptive
analyzes. The percentage of positive subjects (serological and / swab) will be calculated as
the number of positive subjects on the total number of participating subjects. The percentage
of immune subjects will be calculated as the number of subjects with IgG immunoglobulins out
of the total number of participants.These percentages will also be calculated for age and sex
groups and for each characteristic considered relevant.

The logistic regression model will be used to identify demographic / social variables of
predisposition to positivity.