This document is part of a series of discussion notes addressing fundamental questions about COVID-19 and response strategies. These documents are based on the best scientific information available and may be updated as new information comes to light.
Written by Anna Llupià (Hospital Clínic), Israel Rodríguez-Giralt (UOC), Anna Fité (consultant), Lola Álamo (Barcelona Public Health Agency), Laura de la Torre (Hospital Clínic), Ana Redondo (Hospital de Bellvitge), Mar Callau (Blau Advisors) and Caterina Guinovart (ISGlobal), the document addresses the strategy ofcontrol and maximum suppression, known as well as zero-COVID and successfully implemented in South Korea, Taiwan, Singapore, Vietnam or New Zealand.
The objective of this strategy is to keep transmission of the virus as close to zero as possible and ultimately to eliminate it entirely from particular geographical areas. The strategy aims to increase the capacity to identify and trace chains of transmission and to identify and manage outbreaks, while also integrating economic, psychological, social and health-care support to guarantee the isolation of cases and contacts. This approach is also known as "Find, Test, Trace, Isolate and Support” (FTTIS).
The more coordinated, flexible and effective the process, the easier it is to curb the circulation of the virus and keep the number of cases close to zero. Likewise, the lower the incidence of infection, the more effective the strategy is and the easier it becomes to slow the pandemic and mitigate its impacts on health, society and the economy.
As a public health strategy, it is important to distinguish maximum suppression from the strategy of seeking to end the pandemic by gradually allowing the population to become infected. This approach, known as herd immunity, can be a lengthy and costly way to control an epidemic, especially for groups at higher risk of severe disease. It also disproportionately affects the most economically and socially vulnerable individuals and communities. From the standpoint of the precautionary principle, a herd immunity approach is inadvisable because we have a limited understanding of the duration of immunity, the long-term impact of the disease, the behaviour of the disease in successive reinfections, and the associated rates of morbidity and mortality.
The maximum suppression strategy should also be distinguished from containment or mitigation strategies aimed at preventing the health system from being overwhelmed (“flattening the curve”). Even though mitigation strategies are useful when community spread is already very high and impacting the health system, they have an important weakness: they fail to address periods of low transmission or sporadic cases. A mitigation approach therefore runs a high risk of leading to persistent transmission, necessitating endless cycles of lockdowns followed by a relaxation of restrictions—a pattern that cripples the economy, the health system and community engagement.
In contrast, early preventive action to keep transmission under control not only prevents health system overload at every level of care—including care for diseases other than COVID-19—but also protects the physical and emotional health of citizens and health professionals, while also preserving social and economic life and increasing the trust and commitment of society as a whole.
A Solid Detection and Control Infrastructure
A well-sized, robust and coordinated public health infrastructure is crucial to implementing a FTTIS strategy capable of achieving the goal of controlling and suppressing transmission of the virus. It is essential that epidemiological surveillance services have good leadership and the capacity to deliver an adequate response in coordination with health promotion and protection services. In terms of size, tools and coordination, the infrastructure must be capable of guaranteeing that the FTTIS strategy can be implemented quickly, thoroughly and with the necessary support.
An Alert-Level Plan
The strategy of maximum suppression must be accompanied by an alert-level plan devised with input from all sectors of society in order to organise and regulate the various public health measures that must be implemented at different times during the epidemic. These measures include restrictions and, when necessary, stay-at-home orders.
- In a maximum suppression strategy, stay-at-home orders are used during phases with a low number of cases to restore traceability and control. They are implemented briefly, in a targeted manner (only where necessary) and in coordination with other measures.
- In contrast, in mitigation strategies, stay-at-home orders are implemented later, during phases with very high rates of transmission, with the aim of preventing the health system from becoming overwhelmed. They therefore tend to be longer, more restrictive, and have a greater psychosocial and socioeconomic impact. The subsequent need to rapidly offset these impacts causes transmission rates to increase sharply once restrictions are lifted, thus increasing the likelihood of further stay-at-home orders and a loss of public trust in the effectiveness of the measures. If the authorities take too long to issue a stay-at-home order—and especially if such place and lifted too soon—transmission can become persistent, leading overall to a more severe impact on health, the economy and society.
Community involvement is essential to the success of a maximum suppression strategy. For this approach to be feasible, it is crucial to devise a communication strategy capable of generating safe spaces, solidarity and trust. In other words, the communication strategy must be capable of framing the zero-COVID objective as a matter of solidarity and constructive action rather than as a question of individual safety (self-protection), obedience (compliance) or moral responsibility (good behaviour).
Knowledge and Debate
Finally, when implementing a strategy of minimising transmission, we believe it is crucial to promote interdisciplinary, transdisciplinary and multidisciplinary research on the pandemic. Thus far, in keeping with the health-emergency narrative, prioritisation and funding have primarily been directed towards strictly biomedical research, with little attention paid to epidemiological studies, which have essentially consisted of mathematical modelling. There are a number of essential impacts, factors and dynamics—psychological, social, economic, political, cultural, etc.—involved in reducing and preventing the spread of the virus that have not been widely studied thus far. For example, few studies have investigated what sorts of social, geographical and economic conditions—or what places, groups and situations—encourage or discourage people from following public health measures. Similarly, little research has looked into cultures or collective imaginations of risk, how they break down by social groups and how they shape people’s involvement in FTTIS strategies.
It is important to encourage a broader, more transparent and better informed debate about the pandemic, raising the profile of other important angles, voices and sources of knowledge. This debate should encompass not only a broad range of expert knowledge but also the public at large. This pandemic could be an opportunity to strengthen the relationship between science, politics and the public.
Zero-COVID strategy, a more effective epidemiological and community response with fewer negative economic and psychosocial consequences
As the specialised literature shows, societies that learn and collaborate tend to emerge from major crises sooner and stronger. Experiences at the international level suggest that countries pursuing a maximum suppression strategy develop a more effective epidemiological and community response with fewer negative economic and psychosocial consequences than those which adopt a mitigation or herd-immunity strategy.
Although the maximum suppression strategy is challenging and demands a high degree of coordination and social involvement over an extended period of time, it is proving its value as a tool for overcoming this crisis, preparing for future pandemics and fostering solidarity worldwide.