An elderly Dutch woman has become the first known person to die from catching Covid-19 twice, according to experts, raising serious questions about how long immunity and antibodies can last. The woman, 89, suffered from a rare type of bone marrow cancer called Waldenström's macroglobulinemia. Her immune system was compromised due to the cell-depleting therapy she received … However, the researchers said her natural immune response could still have been "sufficient" to fight-off Covid-19, as the type of treatment she received for cancer "does not necessarily result in life threatening disease."