evidence: While an intact, competent immune system may optimize efficacy of a vaccine, routine use of cytotoxic chemotherapy and subsequent myelosuppression presents a logistical challenge for patients undergoing cancer treatment. A recent prospective study compared immune responses with a SARS-CoV-2 mRNA vaccine between patients with solid tumours on cytotoxic, antineoplastic agents and participants without a cancer diagnosis6. Neutralizing antibodies against SARS-CoV-2 increased after sequential vaccine doses in patients with cancer. However, this group receiving cytotoxic chemotherapy, in contrast to the control participants, experienced less of an increase specifically in T cells following vaccine administration.