Modelling SARS-COV2 Spread in London: Approaches to Lift the Lockdown

Abstract

Objective: To use mathematical models to predict the epidemiological impact of lifting the lockdown in London, UK, and alternative strategies to help inform policy in the UK.

Methods: A mathematical model for the transmission of SARS-CoV2 in London. The model was parametrised using data on notified cases, deaths, contacts, and mobility to analyse the epidemic in the UK capital. We investigated the impact of multiple non pharmaceutical interventions (NPIs) and combinations of these measures on future incidence of COVID-19.

Results: Immediate action at the early stages of an epidemic in the affected districts would have tackled spread. While an extended lockdown is highly effective, other measures such as shielding older populations, universal testing and facemasks can all potentially contribute to a reduction of infections and deaths. However, based on current evidence it seems unlikely they will be as effective as continued lockdown. In order to achieve elimination and lift lockdown within 5 months, the best strategy seems to be a combination of weekly universal testing, contact tracing and use of facemasks, with concurrent lockdown. This approach could potentially reduce deaths by 48% compared with continued lockdown alone.

Conclusions: A combination of NPIs such as universal testing, contact tracing and mask use while under lockdown would be associated with least deaths and infections. This approach would require high uptake and sustained local effort but it is potentially feasible as may lead to elimination in a relatively short time scale.

Fig. 1

Structure of the model

Fig. 2

COVID-19 in London's general population. The figure shows the difference between number of notified infections and deaths with (solid line) and without (dotted line) lockdown and calibration to available data (circles).

Fig. 3

Numbers of (a) infections and (b) cumulative deaths in London with and without the current lockdown simulated for 547 days. The solid line represents current conditions. The dotted line (:) shows results if current lockdown were lifted on 8^th May. a. Infections b. Cumulative deaths

Fig. 4

Numbers of (a) infections and (b) cumulative deaths in London with universal testing, facemask use and contact tracing from the 8^th May under lockdown. We compared the scenario of a prolonged lock-down with no additional control interventions (solid line), to the prolonged lock-down with weekly universal testing of the whole population (dotted line (:)), to the addition of facemask usage by isolated positive cases and face coverings by the general population, dotted line (-.), and the addition of tracing and isolation of contacts of positive cases (dotted line (-*). a. Infections b. Cumulative deaths