There are still large uncertainties around the virus, the effectiveness of different policies and the extent to which population adopts risk reducing behaviours? Intensive measures might have to be maintained/re-triggered until a vaccine is available.

1. Timing and width of peak uncertain due to:
• Stochasticity in early dynamics
• Heterogeneity in contact patterns
• Spatial variation
• Uncertainty in key epidemiological parameters
Social distancing flattens curve
Risk of resurgence
following lifting of
interventions
0 1 2 3 4 5 6 7 8 9 10 11 12
Months since transmission established
Measures have been introduced to reduce transmission of the
virus and flatten the epidemic curve. However, there is a risk of
resurgence when measures are lifted
Cases
being
reported
Source: Anderson, R M, H Heesterbeek, D Klinkenberg and T D Hollingsworth (2020), "How will country-based mitigation measures influence the course of
the COVID-19 epidemic?”, The Lancet (online first, 9 March).

2. Intensive measures (e.g. closure of schools, social distancing
of population) might need to be maintained until a vaccine
becomes available

3. It could take 18 months before a vaccine is available

4. 4
Imperial College report (Ferguson et al.) proposed adaptive
hospital surveillance-based triggers for switching on/off
population-wide social distancing and school closure
Illustration of adaptive triggering of suppression strategies
Policy
triggering
(blue)
Weekly ICU
incidence
(orange)
Weekly intensive
care unit (ICU)
cases
Source: Impact of non-pharmaceutical interventions (NPIs) to reduce COVID-19 mortality and healthcare demand (Imperial College COVID-19 Response
Team – 16 March 2020)
Mar-20 May-20 Jul-20 Sep-20 Nov-20 Jan-21 Mar-21 May-21 Jul-21 Sep-21 Nov-21

5. FINAL
There are large uncertainties around the virus, the
effectiveness of different policies and the extent to which
population adopts risk reducing behaviours (Ferguson et al)
Some consider that the outbreak can be stopped completely with no resurgence if measures
are taken early in a multiscale approach, e.g. testing, contact tracing allowing isolation of
infected prior to symptoms, and local lockdowns (C. Shen, N. Taleb, Y. Bar-Yam).
In any case, plans and ways of working will need to be adapted to meet the challenge.

6. References
Anderson, Heesterbeek, Klinkenberg and Hollingsworth, "How will country-based
mitigation measures influence the course of the COVID-19 epidemic?”, The Lancet
(online first, 9 March 2020)
Ferguson et al., Impact of non-pharmaceutical interventions (NPIs) to reduce
COVID-19 mortality and healthcare demand (16 March 2020)
Shen, Taleb N, Bar-Yam, Review of Ferguson et al “Impact of non-pharmaceutical
interventions...” (17 March 2020)