Influenza predictions using school-type and grade-specific absences
We compared the performance of different school-types (elementary, middle, and high school) and grade-specific absences in seasonal models. Elementary school models had lower relMAEs compared to middle and high school models across validations (Supplemental Table 6). Given varied model performance across school types, we also considered one-week lagged grade-specific all-cause absences in seasonal models to assess heterogeneity in predictions by grades.
Univariate analyses found K, 1, 2, 3,4th and 5th grade absence models had lower MAEs than (individual) middle school and high school grade-specific absence models, particularly in leave 20% of schools’ out validation (Figure 3A). Multivariate grade-specific absence models also had lower MAEs relative to seasonal models across three cross-validations (Figure 3B). We observed consistently lower relMAEs for kindergarten-specific absences (relMAE: 0.91, 0.98. 0.92 in three validations). Overall, middle and high school grade-specific absence models did not decrease MAEs relative to seasonal models, although 8, 9, & 10th grade models in leave 20% of weeks out and 6th grade models in leave 20% schools out had lower MAEs.
We investigated whether absenteeism can be used to create more accurate predictions of virologically confirmed influenza only in school aged children, we built models of virologically confirmed influenza only in those 5-17 years old, rather than of all ages. We found modest improvements in two of three validations when including absences compared to not using absences in models that incorporated week of year, relative humidity and temperature. Predictions were more accurate when predicting virologically confirmed influenza in children then when predicting all ages.