Prevention, Efficacy and Safety of BCG Vaccine in COVID-19 Among Healthcare Workers

The study design is a randomized, double-blinded, placebo-controlled clinical trial. Age stratified randomization (\<45 years and\> 45 years) was performed using permuted blocks with allocation concealment. The sample size is 908 patients. 454 patients in each stratum (227 with placebo and 227 with BCG vaccine). Eligible participants will be healthcare professionals over 18 years of age who are in contact with patients with COVID-19, with negative IgG and IgM antibodies results for SARS-CoV-2 prior to their inclusion and sign the informed consent. After signing the informed consent, the participants will be randomized 1:1 to the intervention group (BCG vaccine) or control (placebo), a medical history will be performed, and a blood plasma sample will be obtained to determine specific antibodies against SARS-CoV-2. The patients will be followed up for 6 months after the application of the vaccine, they will be contacted by phone every two weeks in order to identify the adverse effects of the vaccine (30 days after the application) as well as to identify symptoms of COVID-19, in addition, follow-up visits will be carried out at the third and sixth months, in each of these visits a blood plasma sample will be obtained and IgG and IgM antibodies will be measured. Statistical Analysis Type: By intention to treatment