CTLA4 and COVID-19: However, in case of combined immune checkpoint inhibitor therapy (anti-PD-1, anti-PD-L1, anti-CTLA-4), the amount of immune-related adverse events might be increased.31 Antibody response after the COVID-19 vaccination was shown to be adequate in a trial comparing the response of the COVID-19 vaccination in patients with a solid tumor receiving chemotherapy, immunotherapy, or chemo-immunotherapy compared with healthy controls.32