Table 3

School clusters of COVID-19, South Korea, February-December 2020

VariablesKindergartensPrimary schoolsSecondary schoolsTotal
N (%)N (%)N (%)N (%)
Total schools (n)87056120559020 415
 Schools with 0 case8444 (97.0)3747 (61.2)2683 (48.0)14 874 (72.9)
 Schools with ≥1 case211 (2.4)1430 (23.4)1811 (32.4)3452 (16.9)
 Schools with ≥2 cases50 (0.6)943 (15.4)1096 (19.6)2089 (10.2)
School clusters (n)*2190196307
 Student index case7 (33.3)18 (20.0)39 (19.9)64 (20.8)
 Staff index case4 (19.0)11 (12.2)17 (8.7)32 (10.4)
 Unidentified index case10 (47.6)61 (67.8)140 (71.4)211 (68.7)
Median SIR (range)†1.54 (0.43–8.33)0.25 (0.11–3.25)0.41 (0.08–8.15)0.41 (0.08–8.33)
  • *Documented potential transmission within schools identified as of December 2020.

  • †Secondary infection rate in students in corresponding schools.

  • SIR, secondary infection rate.