P.A. post-infection immunity in individuals, initial data in animal models suggest that illness and vaccination confer immune safety [1,2]. It is generally approved that neutralising antibodies TC-H 106 (Nabs) perform a dominant part in the safety against coronaviruses, as previously shown with SARS and MERS [3,4]. The part of humoural immunity is definitely further supported by (i) the relatively high levels of antibody reactions to the surface (spike) protein that mediates access into sponsor cells [5] and (ii) the restorative GLP-1 (7-37) Acetate efficacy of passive infusion of convalescent plasma in individuals with COVID-19 [6,7]. Therefore, it will be TC-H 106 crucial that long term TC-H 106 COVID-19 vaccines generate a protecting humoural immune response, including Nabs. Recent data suggest that individuals with cancer, notably those with haematologic malignancies, are more susceptible to suffer severe complications from SARS-CoV-2 illness [8,9]. It is assumed that immunocompromised individuals generally will also be at improved risk of severe COVID-19. Therefore, it will be of particular importance for these individuals to benefit from an effective vaccine as TC-H 106 soon as it becomes available. Yet some of them may also be less likely to benefit from such a vaccine, especially those treated with anti-CD20 monoclonal antibodies. These antibodies (including rituximab, obinutuzumab, ofatumumab?and ocrelizumab) are widely used in individuals with haematologic malignancies and autoimmune disorders, including B-cell lymphoma, chronic lymphocytic leukaemia, immune thrombocytopaenia, rheumatoid arthritis, antineutrophil cytoplasmic antibody-associated vasculitis, systemic sclerosis and systemic lupus erythematosus. Anti-CD20 antibodies induce quick and long term B-cell depletion. The half-life of rituximab is definitely 20.8 days, but recovery of B cell counts usually starts only 6C9 months after the completion of therapy, and normal levels are obtained after 9C12 months [10]. The continuous period of rituximab-induced B-cell depletion might compromise the immune system, which may be the mechanism of action of anti-CD20 antibodies in antibody-mediated autoimmune diseases. Consistent with the immunosuppressive effect of anti-CD20 antibodies, rituximab has been associated with a risk of reactivation of latent viruses, especially hepatitis B computer virus illness and progressive multifocal leukoencephalopathy caused by reactivation of latent JC computer virus. Anti-CD20 treatments also result in impaired secondary humoural immune responsiveness to vaccination. Indeed, B cells are required for the development of humoural immune reactions to neoantigens, and depletion of B cells following rituximab seems to reduce humoural immune reactions to neoantigens, of which COVIDS-19 is definitely one. Several studies showed a blunted vaccine response after vaccination in individuals with lymphoma [[11], [12], [13], [14]] or autoimmune disorders [[15], [16], [17], [18]] treated with rituximab. Both T cellCdependent and self-employed reactions have been shown to be significantly impaired for at least 6 months after rituximab treatment [18]. Therefore, anti-CD20 therapy may dramatically and durably impair the humoural response to vaccination. For these reasons, most recommendations recommend to wait for at least 6 months after rituximab infusion to perform vaccination. Given the above considerations, and acknowledging that this remains purely theoretical at this point, there is a significant plausible risk that anti-CD20 treatments may abrogate or diminish the future efficacy of a vaccine against SARS-CoV-2. Regrettably, the individuals receiving anti-CD20 therapies will also be those who are the most in need TC-H 106 of a protecting immunity against COVID-19. Consequently, although life-saving anticancer treatments should be managed [19], we suggest that physicians carefully weigh the risk/benefit percentage of anti-CD20 therapy in individuals currently considering or receiving such treatment, especially individuals in whom anti-CD20 therapy is not expected to improve overall survival (for example, maintenance therapy for follicular lymphoma). If a timeframe of 6 months is necessary after the last infusion of anti-CD20 before effective vaccination, and if a vaccine is definitely expected to become available early 2021, it will soon be time to consider discontinuing anti-CD20 therapy for individuals who may tolerate this interruption. This is particularly true if anti-CD20 therapy is not urgent, potentially dispensable or replaceable with option therapies, or if the medical benefit does not outweigh the risk of COVID-19 illness in these high-risk individuals. Further insights concerning this potential risk may come from studies evaluating the pace of seroconversion in individuals who experienced COVID-19 after receiving anti-CD20 therapy. Author contribution All authors published and examined the manuscript. Conflict of interest statement R.H. reports receiving honoraria from Bristol-Myers Squibb, MSD, Gilead, Kite, Roche, Novartis, Janssen, and Celgene. R.L. reports receiving honoraria from Apexigen, Beigene, Forty-Seven, Teneobio, Sutro, Checkmate, Nurix, Dragonfly, Quadriga, GigaGen, Abpro, Spolight, Xcella, Immunoscore,.