The traditional treatment of strep infections has been a seven-day course of antibiotics, either penicillin or erythromycin  However, since many patients stop taking those drugs within three days, reinfection is common in cases where those drugs are prescribed  A new antibiotic requires only a three-day course of treatment
Ttherefore, reinfection will probably be less common in cases where the new antibiotic is prescribed than in cases where either penicillin or erythromycin is prescribed
Some of the people who are allergic to penicillin are likely to be allergic to the new antibiotic.