Regarding febrile, nonhemolytic transfusion reactions (FNHTR), all of the following statements are true except

a. After an initial reaction, recurrence is uncommon.
b. Onset of symptoms occurs during or up to 4 hours after transfusion.
c. Prestorage filtration has been shown to be effective in reducing incidences.
d. Symptoms cause discomfort but are not life-threatening.

Answer: a