Reducing the Mobility of SARS-CoV-2 Variants to Safeguard Containments

COVID-19 DOI: 10.1007/s10272-021-0987-4 Martin Hellwig, Viola Priesemann and Guntram B. Wolff Reducing the Mobility of SARS-CoV-2 Variants to Safeguard Containments Escape variants can cause new waves of COVID-19 outbreaks and put vaccination strategies at risk. To prevent or delay the global spread of these waves, virus mobility needs to be minimised through screening and testing strategies, which should also cover vaccinated people. The costs of these strategies are minimal compared to the costs to health, society and the economy from another wave. When the coronavirus pandemic started in 2019/2020, a number of countries reacted early, closing down public life and reducing private contacts before contagion fully took off. Countries that failed to do this saw large spikes in cases, stretching or overwhelming their medical capacities. Likewise, countries that ignored warning signals of a second wave were hit hard in autumn 2020. A third wave, caused by the more contagious B.1.1.7 SARS-CoV-2 variant, has unfolded. This variant was first recognised in Kent, United Kingdom, from where it spread quickly across the UK and beyond. It spread to countries with more travel to the UK earlier than others. Germany was affected relatively late, while Portugal and Ireland were affected early because of more intensive travel links. Another variant, P1, is also spreading rapidly in Brazil and countries with strong travel connections to Brazil, such as Chile. © The Author(s) 2021. Open Access: This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). Open Access funding provided by ZBW – Leibniz Information Centre for Economics. Martin Hellwig, Max Planck Institute for Research on Collective Goods, Bonn, Germany. Viola Priesemann, Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany. Guntram B. Wolff, Bruegel, Brussels, Belgium. 234 People travelling play a central role in spreading new variants of SARS-CoV-2, with devastating consequences. Stopping a new variant from entering from abroad, or at least slowing it down, would facilitate containment and limit the human, social and economic costs. The experience with B.1.1.7 shows how slower entry of a variant to a country delays the deterioration of the health situation and the introduction of strict and costly lockdowns. Public policy in advanced economies is focusing on vaccination in the hope this will bring down the number of severe cases and deaths while allowing restrictions to be lifted (Dagan et al., 2021). By the end of 2021, large parts of the populations of Israel, Chile, the US, the UK and the EU will have received the vaccine and will be largely immune to the wild strain and some variants of SARS-CoV-2. However, additional waves of contagion must be expected, caused in particular by escape variants against which current vaccines are less effective (McCormick et al., 2021). Even if vaccination continues as currently foreseen, the virus will not be fully eliminated. With incomplete uptake of vaccines, waning immunity and imperfect transmission prevention, it will persist in certain sub-populations (Phillips, 2021). Moreover, in many countries, vaccination is proceeding slowly if at all. The persistent prevalence of the virus in various sub-populations and various places provides a breeding ground for mutations. With advances in vaccination and immunisation, variants that escape the immune response will have an evolutionary advantage. The emergence of escape variants has been documented in several regions, and a similar evolution has also been observed in vitro (Andreano et al., 2020). With an escape variant, contagion persists in the vaccinated population itself and new escape-variant waves Intereconomics 2021 | 4 COVID-19 could spread very quickly if a large part of the population has been vaccinated and moves about without restraint. New restrictions, up to complete lockdowns, might therefore become inevitable, until a new vaccine is developed and administered, and immunisation against the new variant is successful. Any strategy that relies on vaccination only will therefore be insufficient. While everything should be done to speed up the supply of vaccines and their roll-out, a strategy that recognises and slows down the emergence of new variants and limits their spread is needed. Such strategies must encompass the part of the population that has acquired immunity against the wild strain, through vaccinations or through infections. Preparing for this potential danger requires a strategy with three central goals: (1) minimising the rate at which escape variants develop, (2) detecting them early and (3) minimising the mobility of the virus. While all three goals are in principle technically feasible, they run against basic human and social needs, in particular in open societies. Measures to meet the goals must therefore be designed in a way that renders them acceptable. These measures will also be substantially cheaper economically than sustained contagion waves. Minimising the rate at which escape variants develop: Minimising SARS-CoV-2 incidence Low incidence is the best protection against the breeding of new variants. Roughly, the probability that an escape variant emerges is proportional to the number of infected people, and the expected time until a variant emerges is inversely proportional to the number of infected people. Reducing the number of infected people delays the expected emergence of a new escape variant. Low case numbers also have clear advantages for public health, society and the economy (Priesemann et al., 2021; Oliu-Barton et al., 2021). Moreover, at low case numbers, contact tracing contributes efficiently to containment, allowing the health authority to concentrate on the remaining infection chains (Contreras et al., 2021). Lastly, local outbreaks of new variants are detected early and not hidden within a generally high incidence. However, even with low case numbers, escape variants can emerge. Once this has happened, a new variant’s effective reproduction rates in the immunised and non-immunised parts of the population depend not only on the characteristic basic reproduction numbers R0 and R0’, but also on the contact and hygiene behaviour in the two parts of the population. Assuming that the immunised population is less careful about protecting itself, a potent variant could ZBW – Leibniz Information Centre for Economics spread very quickly, because the effective reproduction rate is very high. If such an outbreak is not detected and fought early, development of a new vaccine will be too late, after the wave has taken its toll. Early detection of escape variants: Screening and surveillance The early, local detection of virus variants is important to slow their global spread. Regular screening of a representative sample of the population, as established in the UK for example, (...truncated)