Can herd immunity be achieved without breaking ICUs?

The current COVID-19 pandemic led to the rapid overload of Intensive Care Units (ICUs) in countries where the outbreaks was not quickly controlled. The containment measures put in place to control the outbreaks had a huge social and economic impacts, and countries are looking for strategies to relax these measures while maintaining the R0 close or below 1, in an attempt to safely reach herd immunity. In this paper we analyse the feasibility of reaching herd immunity without saturating ICUs across countries. We provide an online tool, available at www.about-the-curve.net that simulates the time required for such a scenario with a SIR model. For United States, we find that a minimum of 5 months would be required, 22 months for UK, 1 year for Italy and 9 months for Belgium. DisclaimerThe presented results are preliminary and have not been peer-reviewed.

Modeling the COVID-19 outbreaks and the effectiveness of the containment measures adopted across countries

On March 11, 2020, the World Health Organization declared the COVID-19 outbreak, originally started in China, a global pandemic. Since then, the outbreak has indeed spread across all continents, threatening the public health of numerous countries. Although the Case Fatality Rate (CFR) of COVID-19 is relatively low when optimal level of healthcare is granted to the patients, the high percentage of severe cases developing severe pneumonia and thus requiring respiratory support is worryingly high, and could lead to a rapid saturation of Intensive Care Units (ICUs). To overcome this risk, most countries enacted COVID-19 containment measures. In this study, we use a Bayesian SEIR epidemiological model to perform a parametric regression over the COVID-19 outbreaks data in China, Italy, Belgium, and Spain, and estimate the effect of the containment measures on the basic reproduction ratio R0. We find that the effect of these measures is detectable, but tends to be gradual, and that a progressive strengthening of these measures usually reduces the R0 below 1, granting a decay of the outbreak. We also discuss the biases and inconsistencies present in the publicly available data on COVID-19 cases, providing an estimate for the actual number of cases in Italy on March 12, 2020. Lastly, despite the data and models limitations, we argue that the idea of "flattening the curve" to reach herd immunity is likely to be unfeasible.