Second scenario: Physical distancing interventions

A. What would happen if the government had not lifted the first state of emergency before the 2020 summer break?

Results for the first physical distancing scenario in which the 2020 summer break is maintained under extreme restriction policies are illustrated by the red line in Figure 6.7 (for details of its implementation, see section 5.5.2 Second Scenario: Physical distancing interventions A).

According to our results, this intervention would reduce the total number of infections to 76,446 and deaths to 1,609, corresponding to a decrease in the burden of morbidity and mortality of 92-93% by 10^th February 2021 (Figure 6.8).

Although this scenario does not prevent the resurgence of subsequent COVID-19 waves, their magnitude appears to be significantly lower (Figure 6.7a). In particular, in the third wave between mid-December 2020 and January 2021, there would be 938 new cases on 21^st January 2021, in contrast to 10,941 cases reached on the same day under the baseline model. Regarding the impact on healthcare demand, a remarkable reduction is also verified in the need of hospitals and ICUs beds on their peak days, with a decrease of approximately 93% of patients’ admissions in both cases. In this scenario, the number of occupied beds in hospitals and ICUs does not surpass the basal capacity, as shown by the horizontal dotted line in Figure 6.7c-d.

Additionally, the effect of maintaining the 2020 summer under extreme policies would have resulted in Rt

values below its threshold value until the end of August 2020. Lifting this intervention on 25^th August 2020 leads to an increase of Rt to above 1, reaching similar patterns to the baseline model until the end of the simulation (see Figure 6.9).

B. What would happen if schools remained under virtual learning for the 2020/2021 academic year?

Results for the second physical distancing scenario in which schools remain under remote learning for the 2020/2021 academic year are illustrated by the blue line in Figure 6.7 (for details of its implementation, see section 5.5.2 Second Scenario: Physical distancing interventions B).

According to our results, this intervention would mainly avoid the resurgence of the third COVID-19 wave, as we can observe by the decreasing trend depicted in the infection incidence in Figure 6.7a. It would also reduce the magnitude of morbidity, mortality, and the pressure on healthcare services between mid-December 2020 and January 2021.

50 At the end of the simulation, this scenario would lead to a total of 116,760 infections and 2,557 deaths, averting approximately 92-93% infections and deaths compared to the baseline model (Figure 6.8).

Additionally, the effect of virtual learning for the 2020/2021 academic year would lead to a reduction in Rt’s values to at its threshold value and remaining constant to 1 until November 2020. From mid-November 2020 onwards, a remarkable reduction is observed in the evolution of Rt, reaching values below 1 (see Figure 6.9).

Nevertheless, when assessing the potential effect of virtual learning with schoolchildren being cared by people over 60 years old, simulated as an increase of 20%, 50% and 100% additional contacts between these groups, it leads to a general increase in the total number of infections and deaths, as well as an additional number of patients requiring hospitalisations and critical care. In the worst-case scenario, an increment of 100% contacts between schoolchildren and elders would lead to an additional 3,585 infections and 87 deaths, as well as an increase in the maximum number of patients in hospitals and ICUs compared to maintaining virtual learning without additional contacts between these age groups (Table D.1, Appendix D).

C. What would happen if the second state of emergency had not been relaxed by 2020 Christmas?

Results for the third physical distancing scenario in which the 2020 Christmas period is maintained under extreme restriction policies are illustrated by the golden line in Figure 6.7 (for details of its implementation, see section 5.5.2 Second Scenario: Physical distancing interventions C).

According to our results, this intervention would reduce the burden of morbidity and mortality, as well as the impact on the healthcare system of the third COVID-19 wave between mid-December 2020 and January 2021. Notably, it would also have the potential to avoid the resurgence of the third COVID-19 wave, as observed by the decreasing trend depicted in the infection incidence graph (Figure 6.7a) and by the constant Rt value stable at 1 (with a slight decrease to below 1 since January 2021) (Figure 6.9).

In particular, at the peak day of cases, 21^st January 2021, this intervention would result in a total of 2,636 new infections, averting 76% of infections compared to the baseline model. A similar reduction is also obtained on the number of deaths at its peak day. Compared to the baseline model, this scenario would also reduce the healthcare service demand by 71-76% on their peak days and, importantly, would help relieve the healthcare system both in infirmary beds and ICUs.

At the end of the simulation, this scenario projects a total of 592,124 infections and 12,091 deaths, which imply 60% fewer infections and 46% fewer deaths compared to the baseline model (Figure 6.8). By 10^th February 2021, SARS-CoV-2 would have infected nearly 5.7% of the Portuguese population.

51 Table C.2, Appendix C, summarises the numerical results obtained for the three physical distancing scenarios (A, B, C) presented in this subsection compared to the baseline model.

Figure 6.7. Effects of different physical distancing interventions on the evolution of the number of cases (a,b), hospitalisations (c,d), and deaths (e,f) compared to the baseline model between 3^rd March 2020 and 10^th February 2021. The horizontal dotted lines in (c,d) represent the basal beds capacity for COVID-19 patients in hospitals and ICUs, corresponding to 17,700 and 1,021 beds, respectively. Note that the simulations account for 25% of asymptomatic infections. In all panels, the y-axis is plotted in a logarithmic scale.

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Figure 6.8. Fraction of cumulative infections averted % relative to the day upon each scenario is implemented. The results show the fraction of cases averted for each scenario A, B, C (compared to the baseline model with ft = 25%) for each day of our period of study. Note that the fraction of infections averted starts when the intervention is implemented, corresponding to 26^th April 2020 for scenario A, 25^th August 2020 for scenario B, and 22^nd December 2020 for scenario C.

Figure 6.9. Effective reproductive number Rt for the different physical distancing interventions (A, B, C) from March 2020 to February 2021. The dotted horizontal line at y = 1 represents the Rt’s threshold value. Recall that scenario A is implemented on 26^th April 2020 and maintained until 25^th August 2020, scenario B is implemented on 25^th August 2020 and maintained until February 2021, and scenario C is implemented from 22^nd December 2020 to February 2021.