Prevalence and Risk Factors of SARS-CoV-2 Antibody Responses (COVID-19)

- Study design: observational and prospective study with one year of follow-up of the
cohort of workers of the CSdM, including workers of subcontracted companies working in
the Hospital of Mataró (2,300 workers approximately) and with controls at baseline and
at 3, 6, 9 and 12 months.

- Aims: to perform a universal test for all the professionals of the Consorci Sanitari del
Maresme (CSdM) in order to carry out the following objectives:

1. Let them know if they have been exposed to the SARS-CoV-2 virus.

2. Identify asymptomatic carriers of SARS-CoV-2 virus.

3. Develop an immune map of all the professionals to: a) describe the seroprevalence
of SARS-CoV-2 antibodies and their evolution over a year; b) help minimize the risk
of infection in CSdM professionals; c) contribute to the improvement of knowledge
about the infection and the social and occupational factors that affect its spread;
and d) allow in the future to identify the duration of immunity against SARS-CoV-2.

- Time Frame: 1 year.

- Study population: all workers from the healthcare centers of the Consorci Sanitari del
Maresme will be invited to participate by e-mail and by announcements in the corporate
website. A space will be set up on the corporate intranet where workers will be informed
about the study, will be able to give their informed consent and will be able to answer
an electronic questionnaire regarding socio-demographic, clinical and labour personal
characteristics. Once the questionnaire answered, participants will be authorized to
schedule a blood extraction.

- Methods: Prevalence of antibodies against SARS-CoV-2 will be analyzed (IgA, IgM, IgG)
and PCR will be also performed for IgM and IgA positive subjects following this
algorithm:

Serological study:

1. Screening the entire population with total CLIA result (IgA, IgM, IgG) to determine
negatives.

2. ELISA for positives with differentiated IgM, IgA and IgG results.

3. PCR of nasopharyngeal smears on all IgM and IgA + (to determine asymptomatic cases).

There will be other blood samplings and determination points at 3, 6, 9 and 12 months for all
the study participants.