Impact of non-pharmaceutical interventions (NPIs) to reduce COVID-19 mortality and healthcare demand

Neil M Ferguson, Daniel Laydon, Gemma Nedjati-Gilani et al. Impact of non-pharmaceutical interventions (NPIs) to reduce COVID-19 mortality and healthcare demand. Imperial College London (16-03-2020), doi:
https://doi.org/10.25561/77482.

Review written by:

Lily Xu, edited by Ava Kamb

Yellow - Has not been peer-reviewed yet and is not a controlled experiment; however, the Imperial College London is very reputable and the statistical analysis/modeling appears to be sound.

SARS-COV-2 is the most serious respiratory virus since the 1918 H1N1 influenza outbreak. Epidemiological modelling has been used to inform policy in many countries as governments implement new public health measures. The authors examined such measures through a modelling lens to evaluate their efficacy in reducing transmission of the virus. The two categories of interest were mitigation and suppression policies. The goal of mitigation is to “flatten the curve,” or reduce the impact of the epidemic. The goal of suppression is to actively decrease the number of cases and maintain a low level indefinitely. In order to explore the pros and cons of each strategy, the authors modified an individual-based pandemic influenza simulation model to fit COVID-19 conditions. This model used population density, workplace distribution, and census data to predict contact rates. The authors also made certain assumptions for the parameters including, but not limited to: an incubation period of 5.1 days, R0 is between 2.0 and 2.6, and that individuals are immune to reinfection.


The mitigation strategies (case isolation, home quarantine, and social distancing from high risk groups) were comparatively less socially disruptive in comparison to the suppression strategies and would be able to significantly reduce deaths and healthcare demand in just three months of implementation. However, the authors concluded the U.K. and U.S. healthcare systems are simply unable to handle mitigation strategies without increasing their current capacities many times over; too many people would still be getting sick under the mitigation strategies. The authors ultimately concluded that suppression policies (case isolation, population-wide social distancing, household quarantine, and school closure) were the most viable in order to control the flow in and out of the healthcare systems. That being said, the authors do acknowledge that success would still come at a great social and economic cost. In order to prevent a rebound of transmission rates, suppression policies would need to be maintained until a viable vaccine is made widely available.

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