5-day treatment group 10-day treatment group P value 77 46 : 31 6.70 ± 1.93 2.75 ± 1.54 12.95 ± 17.30 22.57 ± 3.03 149 92 : 57 6.80 ± 2.10 2.81 ± 1.24 9.20 ± 11.47 22.02 ± 2.94 Table 1: Characteristics of children with repeated GABHA pharyngitis. International Journal of Pediatrics Characteristics Number of cases Male:Female Age (years) (mean±SD) Frequency of episodes (times) (mean±SD) Interval between preceding and present episodes (months) (mean±SD) Length of follow-up (days) (mean±SD) Total 226 138 : 88 6.77 ± 2.04 2.79 ± 1.35 10.48 ± 13.8 22.20 ± 2.98 5–8 years; SD: 0.91 years). The mean interval from onset of the index infection to onset of subsequent recurrent GABHS pharyngitis was 11.3 days after the initiation of therapy (range: 6–22 days; SD: 4.94 days). The mean number of episodes of repeated GABHS pharyngitis was 2.88 (range: 2–6; SD: 1.36). The mean interval between preceding and present episodes was 10.81 months (range: 0.5–24 months; SD: 8.268 months). There was no recognizable risk factor of recurrent GABHS pharyngitis in the patients, probably due to the limited number of recurrent cases. Bacteriologic treatment failure at the follow-up visit was observed in 7 (9.1%) of the 77 children in 5-day treatment group and in 17 (11.4%) of the 149 children in the 10-day treatment group. There was no signiﬁcant diﬀerence between the two treatment groups (P = .655). The treatment failure rates were 18.2% in the 5-day group and 12.1% in the 10-day group. This diﬀerence was also not statistically signiﬁcant (P = .231). No poststreptococcal sequelae were noted in this study. The characteristics of children in the treatment success group (bacteriologic treatment success with no recurrence) and treatment failure group (either clinical or bacteriologic treatment failure) are shown in Table 3. Ratios of males to females were 1 : 0.73 in the treatment success group (194 children) and 1 : 0.23 in the treatment failure group (32 children). Treatment failure rates were signiﬁcantly aﬀected by gender (P = .011). Mean ages were 6.86 years (range: 2–14 years; SD: 2.12 years) in the treatment success group and 6.24 years (range: 3–9 years; SD: 1.39 years) in the treatment failure group (P = .036). Treatment failure was observed more frequently in the 86 children aged 6 to 7 years (in 22 of the 86 children, treatment failure rate of 25.6%) than in the 66 children aged 2 to 5 years (in 6 of the 66 children, treatment failure rate of 9.1%; P < .001) and in the 74 children aged 8 to 14 years (in 4 of the 74 children, treatment failure rate of 5.4%; P < .001). The mean number of episodes of repeated GABHS pharyngitis in the treatment success group was 2.77 (range: 2–6; SD: 1.36) and that in the treatment failure group was 2.91 (range: 2–12; SD: 1.26), the diﬀerence between the groups not being statistically signiﬁcant (P = .586). The mean intervals between preceding and present episodes were 11.04 months (range: 0.5–79 months; SD: 14.57 months) in the treatment success group and 7.05 months (range: 0.4–27 months; SD: 7.31 months) in the treatment failure group. Although the diﬀerence between the intervals in the two groups was statistically signiﬁcant .775 .728 .768 .089 .203 3 (P = .019), the interval responsible for treatment failure could not be statistically determined. All corresponding strains isolated from the 24 children with positive follow-up cultures both at pre- and posttreat- ments had the same serotype. Six diﬀerent T types were identiﬁed, of which T12 was the most common serotype. In the 8 children with recurrence within the follow-up period, only 4 corresponding strains isolated at pretreatment and at recurrence were available for characterization by serotyping. GABHS with diﬀerent serotype was identiﬁed in one child in the 5-day treatment group but not in other children. 3.2. Discussion. Recurrence of GABHS pharyngitis fre- quently occurs in children after treatment. Approximately 10 to 20% of children have recurrent infection within 1 year of an index infection [5, 11, 17]. Possible explanations for the recurrence are 1) reinfection: new infection with GABHS, and 2) relapse: recurrence of originally persisted GABHS. Although serotyping of GABHS isolates helps to make the distinction, it may be diﬃcult to distinguish between reinfection and relapse. Holm et al. reported that 10-day cephalosporin treatment in children with recurrent GABHS pharyngitis resulted in bacteriologic and clinical cure rates higher than those of 10-day penicillin treatment [18]. In this study, the recurrence rate within 3 weeks after the initiation of therapy was signiﬁcantly higher in the 5- day treatment group than in the 10-day treatment group. However, the diﬀerence between the two treatment groups in rate of bacteriologic treatment failure at the follow-up visit was not statistically signiﬁcant. All corresponding strains isolated at pre- and posttreatments in the 24 patients with bacteriologic treatment failure had the same serotype, indi- cating that the treatment failure might be relapse. Only one of the corresponding isolates in 4 children with recurrence had diﬀerent serotypes, indicating that the treatment failure in this case was reinfection. Test-of-cure timing, follow- up visit in this study, is important in the interpretation of treatment failure rate. It has been suggested that the test- of-cure evaluation should optimally be done within 3 to 14 days after completion of therapy [12]. Although we were not able to rule out the possibility of reinfection with a new strain, the fact that 96% of corresponding isolates during 3- week period had the same serotype in this study suggested that most of the treatment failure cases within 3 weeks were caused by relapse. Age of 6 to 7 years for boys and