A 52-year-old man with mantle cell lymphoma treated with bendamustine and rituximab developed prolonged severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Despite elevated titers of anti-spike IgG antibody, protracted pancytopenia persisted for more than six months. Finally, the anti-SARS CoV-2 vaccine, BNT162b2, was administered, which improved his blood cell count and eliminated the virus. The increased anti-spike IgG titer and lymphocyte count after vaccination suggested that both humoral and cellular immunity acted in coordination to eliminate the virus.