As of December 2021, more than 276 million affected cases and 5 million deaths were reported by the World Health Organization, due to the COVID-19 pandemic [1]. Following the outbreak's beginning, patients receiving treatments impairing their immunity (e.g., chemotherapy; immunosuppressive drugs for solid organ transplantation or inflammatory diseases) were soon recognized as being at increased risk of developing severe forms of COVID-19 [2,[3]]. Although anti-SARS-CoV-2 vaccines have proven to be efficacious in reducing the risk of both severe disease and mortality in the general population [4], emerging evidence has revealed that immunocompromized patients actually display a reduction in vaccine-induced humoral responses [5,6].
