The pronunciation of "efficacy" is changing. Until recently I had only ever heard "EFFicacy". Recently I have heard people being interviewed whose first language was clearly not English, who talked about a vaccine's "effICKacy".
Yesterday I heard the change taking place on air, as someone with a southern English accent who was being interviewed on Radio 4 began to say "EFFic...", then hesitated, started again, and this time said "effICKacy".