OSE Immunotherapeutics announced the positive analysis of the first data of CoVepiT, its prophylactic vaccine candidate against COVID-19, in particular positive interim immunological results on T cell response obtained in 100% of the treated population, with in parallel a resolution of local indurations observed during vaccination. Last July, the company voluntarily suspended the recruitment and administration of CoVepiT in the Phase 1 clinical trial as a precaution due to a limited number of adverse reactions (nodule-like indurations at the injection site) grade 1 and a grade 2 adverse reaction in one participant. Since then, the data have been analyzed regularly with the Independent Safety Monitoring Committee in charge of evaluating the safety of the trial and the Ghent (Belgium) investigation center. The indurations were resolved within a few weeks for most of the participants (without systemic reaction, without fever, nor inflammation, without local ulceration) and the follow-up continues to show a good safety profile. This profile, with frequent indurations, is close to that of vaccines inducing T cell responses (1;2;3) and is regularly linked to this T cell mechanism of action. The immunological response was measured on the eight healthy volunteers who received CoVepiT, showing the expected efficacy at six weeks after the injection, the primary endpoint of the phase 1 trial, with good immunogenicity of the T cells against the viral epitopes. Interferon-gamma responses measured by Elispot was observed in 100% of participants, from the 22nd day to the 6th week. These immunological results are significantly better than those obtained in convalescent patients and confirm the interest and the mechanism of action of the vaccine on the T cell response. In addition, new preclinical studies have shown that the intensity and the quality of the immunogenicity of the T cells induced by the CoVepiT vaccine were not altered by concomitant immunosuppressive treatments such as antimetabolites (mycophenolate mofetil, MMF, inhibiting immunosuppressant proliferation of B and T cells) or by a strong depletion of B cells producing antibodies (observed with rituximab, used in autoimmune diseases and certain cancers). The interest in generating T cells is enhanced especially for immunocompromised patients with weak antibody responses despite repeated administration of current registered vaccines.