Introduction: Cross-reactivity caused by similar viral antigens leading antibody production are observe in several pathologies including SARS-CoV2 infection. This seems to occur with the measles, rubella and mumps viruses contained in the MMR vaccine. The cross-reactivity MMR immunization within SARS-CoV2 antigens may be an alternative vaccine complement to specific vaccines for SARS-CoV2. Objective: To investigate the ability of MMR antigens to induce the proliferation of B cells able to produce antibodies against SARS-CoV2 antigens in convalescent Covid-19 patients and vaccinated subjects. Methodology: Cross-sectional study that has recruited 24 donors so far, with positive and/or negative SARS-CoV2 serology and who have or do not serological MMR signature. PBMC cultures were labeled using MitoTracker™ (Invitrogen), upon different MMR concentration. Herein, cell proliferation by FACS and S1, S2 and N-protein of SARS-CoV2 antibodies measured by ELISA. Results: B cells from SARS-CoV2 vaccinated and/or convalescent individuals for undergo proliferation when stimulated with 25 and 50 IU/mL of MMR. These cells produce antibodies of the IgG class against S2 and N- protein of SARS-CoV2. MMR (+) Covid19(-) control group showed proliferation with production of anti-SARS- CoV2 antibodies. Conclusion: MMR antigens induces B cells proliferation and antibodies that present cross- reactivity against SARS-CoV2 S2 and N-protein.