A 48-year-old woman on ICU with severe sepsis has a serum procalcitonin (PCT) of 12.5 µg/L at the start of antibiotic therapy. After 5 days, her PCT has fallen to 1.2 µg/L (>80% reduction from peak). She is afebrile and clinically improving. According to PCT-guided antibiotic cessation protocols, what is the recommended action?