Low case numbers enable long-term stable pandemic control without lockdowns.
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Citations
The challenges of containing SARS-CoV-2 via test-trace-and-isolate.
Is there no alternative
Elimination versus mitigation of SARS-CoV-2 in the presence of effective vaccines.
Elimination versus mitigation of SARS-CoV-2 in the presence of effective vaccines
How to coordinate vaccination and social distancing to mitigate SARS-CoV-2 outbreaks
References
Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine.
Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1.
The Mathematics of Infectious Diseases
The Incubation Period of Coronavirus Disease 2019 (COVID-19) From Publicly Reported Confirmed Cases: Estimation and Application.
Safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) against SARS-CoV-2: an interim analysis of four randomised controlled trials in Brazil, South Africa, and the UK.
Frequently Asked Questions (16)
Q2. How can the authors estimate the value of in the integration routine?
The explicit value of φ can be obtained numerically in the integration routine, or estimated trough the use of the equilibrium values of the differential equations, φ = IH,s ∞ IH∞(as implemented in their code).
Q3. How do the authors determine if a system can reach an equilibrium at low case numbers?
Low case numbers enable long-term stable pandemic control without lockdownsBetween the scenarios of eradication of the disease or uncontrolled spreading, the authors find a regime where the spread reaches an equilibrium at low daily case numbers.
Q4. How do the authors determine if a lockdown is necessary to re-establish?
In conclusion, to re-establish control, a lockdown needs to be strong enough to reach equilibrium within a few weeks, or it fails almost completely.
Q5. How much contact reduction is required to maintain the (meta-)stable regime?
If case numbers are sufficiently below the TTI capacity limit, the required contact reduction to maintain the (meta-)stable regime is only kcritt = 39 % (95% confidence interval (CI):[24, 53]).
Q6. What is the effect of TTI measures on case numbers?
As the effectiveness of TTI measures depends on daily infections, case numbers can seemingly explode when the (hard-to-estimate) TTI capacity limit is exceeded.
Q7. how many infections are found in the symptom-driven and random testing?
(35)If both symptom-based and random testing take place simultaneously, the number of discovered infections is given byN test = λrIH + λsIH,s (36)Further, assuming that after reaching N testmax, the testing rates at the overhead pool-sizes would decrease to λ′s and λ′r, respectively, for symptom-driven and random testing.
Q8. How can the authors express Rt in terms of the basic reproduction number?
It can be expressed in terms of the effective reproduction number Rt:ϱ = 1 − 1 Rt . (27)In the context of their model, Rt can be expressed in terms of the reduction of contagious contacts kt and the basic reproduction number R0; Rt = (1 − kt) R0.
Q9. How much contact reduction is necessary to stay within the metastable regime?
maintaining a moderate contact reduction while not in lockdown (knLD = 40 %) is sufficient to stay within the metastable regime — if lockdowns are enacted such that case numbers stay below the TTI capacity (Fig. 4 b, yellow line).
Q10. How many days of lockdown are necessary to bring back cases below TTI capacity limit?
If started right after crossing the threshold, in principle, only a few days of lockdown are necessary to bring back case numbers below TTI capacity limit.
Q11. How did you study the stability of the governing differential equations?
S2.2 Linear stability analysis and uncertainty propagationFor analysing the stability of the governing differential equations, namely, whether an outbreak could be controlled, the authors studied the linear stability of the system.
Q12. How long does the lockdown DL take?
The duration of the lockdown DL, namely, the time-frame between the start of the restrictive measures and the beginning of their relaxation, is measured in weeks, and its default length – for analysis purposes – is four weeks.
Q13. What is the definition of random testing?
Random testing is defined here as applying tests to individuals irrespective of their symptom status, or whether they belonging to the contact-chain of other infected individuals.
Q14. How much contact reduction is required to maintain the stable regime?
if case numbers exceed the TTI capacity limit, a considerably stronger contact reduction of kcritt = 58 % (95% CI: [53, 62]) is required to reach the stable regime (Fig. 2 b, Fig. S4 and Table S3).
Q15. What is the simplest way to determine the tipping point between controlled and uncontrolled outbreaks?
To derive the tipping point between controlled and uncontrolled outbreaks (e.g. critical, minimal required contact reduction kcritt for both stability and metastability), and to plot the stability diagrams, the authors used the @fzero MATLAB function, and the linear approximation of the system of DDE (2)–(6) for the SM ≈ 1 limit.
Q16. How does the model transfer infected individuals from the hidden to the quarantined infectious pools?
In their model, random testing transfers infected individuals from the hidden to the quarantined infectious pools with fixed rate λr, irrespective of them showing symptoms or not.