Under FDA emergency-use authorization, doctors successfully resolved COVID-19 in a seriously ill, immunodeficient woman using a very high-neutralizing antibody-titer convalescent plasma from a recovered COVID-19 patient. However, further study suggested that use of convalescent plasma may not be warranted in many cases, for two reasons: 1) titer levels are too low in many convalescent plasmas, and 2) there are high endogenous neutralizing antibody titers already present in COVID-19 patients prior to infusion.