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Table 3 Summary of best estimates and ranges of variables used in the nationwide representative School Building Archetype (SBA) model

From: Estimating the nationwide transmission risk of measles in US schools and impacts of vaccination and supplemental infection control strategies

Parameter Primary School
Best-Estimate [Range]
Secondary School
Best-Estimate [Range]
Reference
No. of educational institutions in US 2015–2016 88,665 26,986 NCESa
No. of Index case/s 1 1 Assumption
Quanta generation rate (quanta / hour) 1925 [1185–3345] 2765 [1430–5140] This Studyb
No. of enrolled students before outbreak 513 [175–825] 854 [245–1394] NCESc
Infection period in school (day) 3 [2–4] 3 [2–4] Literatured
Portion of unvaccinated students 9% [8–10%] 9% [8–10%] CDCe
Portion of students with ≥2-dose vaccination 91% [90–92%] 91% [90–92%] CDCe
No. of students in infector’s classroom 21 [18–26] 23 [18–30] SASSf
Occupancy density of classroom (m2/person) 4 [3–5] 4 [3–5] DOEg
Occupancy density of common area (m2/person) 1.39 [1.04–1.74] 1.39 [1.04–1.74] DOEg
Average time spent in school (mins) 400 [375–425] 400 [375–425] SASSh
Average time spent in common area (mins) 20 [15–30] 30 [20–45] NFSMIi
Heating and cooling periods in US schools (day) H: 200 & C: 90 H: 200 & C: 90 Assumptionj
HVAC system type See Table 4 See Table 4 CBECSk
HVAC recirculation rate in classrooms (per hour) 6.4 [3.3–8.5] 6.4 [3.3–8.5] Literaturel
Outdoor air ventilation in classrooms (L/s-person) 6.7 [4.0–9.5] 6.7 [4.0–9.5] ASHRAEm,
Outdoor air ventilation in common area (L/s-person) 4.9 [4.7–5.1] 4.9 [4.7–5.1] ASHRAEm
HVAC runtime for applicable systems 1 1 Assumption
Air filter removal efficiency (%) 72% [44–86%] 72% [44–86%] NAFAn
Infiltration rate (1/h) 0.31 [0.12–0.49] 0.31 [0.12–0.49] DOEg
Deposition rate of measles bio-aerosols (1/h) 1.7 [1.0–2.7] 1.7 [1.0–2.7] Literatureo
Inhalation rate (m3/day) 12.96 [11.34–14.53] 15.53 [13.93–17.45] EPAp
  1. aU.S. Department of Education, National Center for Education Statistics (NCES), [66]; Table 105.50 “Number of educational institutions, by level and control of institution: Selected years, 1980–81 through 2015–16”
  2. bThe method explained in “Back-calculating quanta generation rate” Section and results are provided in “Estimates of quanta generation rate” Section
  3. cU.S. Department of Education, NCES, [67]; Table 5 “Average student membership size of regular public elementary and secondary schools with membership, by instructional level, membership size of largest and smallest school, and state or jurisdiction: School year 2009–10”
  4. dBased on existing epidemiological literature [68,69,70]
  5. eCenters for Disease Control and Prevention (CDC) [71, 72]
  6. fU.S. Department of Education, NCES, Schools and Staffing Survey (SASS) [73]; Table 7. “average class size in public primary, middle, and high schools is listed by classroom type and state in school year 2011–12”
  7. gU.S. Department of Energy commercial reference building models of the national building stock, [48]; Appendix A
  8. hU.S. Department of Education, NCES, SASS, [74]; “Average number of hours in the school day and average number of days in the school year for public schools, by state: 2007–08”
  9. iNational Food Service Management Institute [75]
  10. j200 days of heating season from October to mid-April and 90 days of cooling seasons in one school academic year
  11. kU.S. Energy Information Administration, Commercial Buildings Energy Consumption Survey [76, 77]
  12. lBased on Polidori et al. and Chan et al. studies [78, 79]
  13. mThe American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 62.1–2016 Ventilation for Acceptable Indoor Air Quality (2016) [80]
  14. nNational Air Filtration Association [81]
  15. oBased on Azimi and Stephens study [54]
  16. pU.S. EPA Exposures Factors Handbook [63]