We can use the same framework to consider the effect of closing workplaces. As with closing schools, we assume that individuals who are not at work spend their former work-time at home, while time spent circulating in the community is unchanged. Figure 4.7 shows the epidemic curve under no intervention (red), with schools closed (blue), and with 50% of workplaces closed in addition to all schools (green). Closing schools and 50% of workplaces is sufficient to prevent spread of infection for R0 equal to 1.5.
- Figure 4.7 The epidemic curves for the SEIRH with no intervention (red dotted line), closing schools (blue dashed line) and also closing 50% of workplaces (green solid line) for R0 values of 1.5, 2.5 and 3.5 and assuming influenza attack rates as in 1968-69. The graph corresponding to R0 = 1.5 and the intervention ‘closing schools and 50% of workplaces’ is not shown in the top left plot as this intervention is sufficient to eliminate the infection.
The impact that school closure together with the closure of non-essential workplaces has on the R, is illustrated in Figure 4.18 (see below). This combination of interventions reduces the effective R considerably. Specifically, by adding closure of schools and 50% of workplaces to the default antiviral strategy (whereby diagnosed patients get AVs for treatment, while doctors and flu-dedicated HCWs get AVs for prophylaxis, with the latter using PPE as well), disease elimination is achieved for values of R0 that are double those that are able to eliminate the infection with the default strategy alone.
The effectiveness of closing schools and workplaces depends on the age-specific attack rates, but shows similar relative effects across reproduction numbers of 1.5 to 3.5. When the attack rates across age classes are relatively flat (as in 1968-69), closing schools reduces the reproduction number to around 85% of its base value. Additionally closing 50% of workplaces reduces the reproduction to approximately 70% of the base value, and when all workplaces are closed, the reproduction number is reduced to around 55% of its base value. In contrast, if the attack rates in school children are particularly high (as in 1957), closing schools reduces the reproduction number to approximately 68% of its base value, while closing workplaces reduces this further to around 58% with half workplaces closed, and 48% with all workplaces closed. The benefit of closing schools is greater when children are particularly at risk of infection, but in this case, closing workplaces provides less additional benefit than when attack rates are similar across age groups.