Vaccine rollout has started in many countries. In Italy, the Covid-19 vaccine used at the moment is the mRNA-based BNT162b2 and is given to Hospital employers. The investigators undertake this study to monitor IgG evolution after vaccination in the participant hospital settings, which includes 500 subjects.

Vaccine rollout has started in many countries. In Italy, the Covid-19 vaccine used at the moment is the mRNA-based BNT162b2 and is given to Hospital employers.

The investigators undertake this observational study to monitor antibody evolution after vaccination in a hospital setting. The primary endpoint is serum IgG at the first month of 2nd jab, and at 3, 6, and 12 months afterward.

As secondary measures, nasopharyngeal swabs are included, at fortnight intervals to detects the spike protein antigen, in the event that putative vaccine inefficacy would expose the health personnel to Covid-19 disease with potential spreading to inpatients.

Further, clinical signs and symptoms are monitored at the weekly interval in the context of adverse reactions/events.

Inclusion Criteria:

• Hospital employers vaccinated against Sars-Cov2

Exclusion Criteria:

• none

Health care, administrative, and technical workers of ICOT-Sapienza University Hospital