1. Sign the Informed Consent before initiating the selection procedures.
2. Health system workers working in contact with subjects potentially infected with SARS-CoV-2.
3. People ≥ 18 years.
4. Availability to meet the requirements of the protocol.
5. Negative Rapid Serological Test of SARS-CoV-2
You may not be if
1. Previous SARS-CoV-2 infection
2. Pregnancy or breastfeeding.
3. Suspected of active viral or bacterial infection.
4. Symptoms compatible with COVID-19, despite a negative PCR test.
5. Vaccination in the last 4 weeks or planned vaccination during the study period, regardless of the type of vaccine.
6. Participation in a research that requires experimental intervention (does not include observational studies) in the previous month before signing the Consent or during the study.
7. Severely immunocompromised people. This exclusion category includes:
1. Subjects with human immunodeficiency virus (HIV-1).
2. Neutropenic subjects with less than 500 neutrophils / mm3.
3. Subjects with solid organ transplantation.
4. Subjects with bone marrow transplantation.
5. Subjects undergoing chemotherapy.
6. Subjects with primary immunodeficiency.
7. Severe lymphopenia with less than 400 lymphocytes / mm3.
8. Treatment with any anti-cytokine therapy.
9. Oral treatment with steroids, defined as daily doses of 10 mg prednisone or equivalent for more than 3 months.
8. Malignancy, or active solid or non-solid lymphoma from the previous two years.
9. BCG vaccination in the last 10 years.
10. Treatment with Manremyc® for the last 6 months.
11. Chloroquine or hydroxychloroquine administration in the last two weeks.
12. Direct involvement in the design or execution of the MANRECOVID19 clinical trial.
13. Retirement, transfer, long-term leave (\> 1 month) due to scheduled surgery or any other event that makes it impossible to work in person at your health center during the months following the recruitment to the study.
14. Employee at the health center \<22 hours per week.
15. Do not have a smartphone.
16. Detection by the investigator of lack of knowledge or willingness to participate and comply with all requirements of the protocol.
17. Any other findings that, at the discretion of the investigator, may compromise compliance with the protocol or that may influence significantly the interpretation or the results of the effects of probiotic.
