What are the challenges and options for East Asian countries that pursued “elimination” strategies?
Twenty months into the covid-19 pandemic, and many countries in East Asia are now looking forward past the current “zero covid” policy that has characterised the pre-vaccine phase, and towards “sustainable endemicity.” This has formed part of a renormalisation policy goal since covid-19 vaccines have become available. We would go so far as to say that accepting that covid-19 will become endemic could ultimately be the only foreseeable exit for all countries.
Vaccines that produce population immunity are the bridge between zero covid policies and sustainable endemicity. Whereas in much of Europe and the Americas natural infection and recovery already provide a substantial level of acquired immunity, countries in the eastern hemisphere, including East Asia and Australasia, have minimal seroprevalence and so are necessarily much more reliant on vaccination in order to transition towards endemicity. [1-3]
Achieving high vaccination coverage before relaxing elimination measures will minimise the impact of any subsequent community spread of covid-19. High covid-19 vaccine coverage would provide protection at the individual, as well as population level. While breakthrough infections may occur in fully vaccinated individuals, the vaccines could help to prevent severe symptoms by shifting the severity of illness to resemble more that of seasonal influenza, and therefore hopefully protecting the healthcare system from overwhelming demand. [4,5]
However, global vaccine inequalities remain concerning.  So far, richer countries have vaccinated more of their population and the lack of vaccinations available to low and middle income countries is a risk. The covid-19 vaccination rate is very low in many countries, particularly countries with GDP per capita lower than US$4000. In addition, vaccine hesitancy is a challenge to achieving high coverage. 
In some locations that have succeeded in maintaining covid-19 elimination, the very success of this is now a cause of vaccine hesitancy because of the perceived lack of threat currently posed by covid-19. Insufficient vaccine coverage makes it difficult to plan a timeline for relaxing restrictions because of the danger that covid will pose after restrictions are relaxed, if the majority of the population are not vaccinated.
The Global Health Security (GHS) Index 2019, which indicates the pre-pandemic preparedness of 195 countries, did not strongly correlate with the actual impact that the covid-19 pandemic had on different countries in terms of total number of cases, deaths, and tests performed and recovery rate.  Some East Asian countries, such as China and Japan, which were classified as being more prepared for a pandemic, have handled the ongoing pandemic relatively well with low cumulative cases per million, while some of the most prepared countries, for example the US and UK, have had a much higher number of confirmed cases. However, the Index correlates with actual vaccine uptake.
Recently, the Bloomberg ranking of covid resilience showed that the US was ranked No. 1, when considering progress made in reopening, covid status, and quality of life, while China, UK, and Japan were ranked 8th, 9th and 23rd.  However, it is noteworthy that the cumulative cases have increased substantially in most countries (including US and UK) from the time of the first vaccines becoming available. We need to consider if it is too soon to relax restrictions in East Asia when the cumulative vaccinations have reached only around 100 per hundred people (representing on average fewer than 50% population are fully vaccinated) in the region. Relaxing covid restrictions could be particularly risky for unvaccinated or not fully vaccinated individuals. This concern may be compounded if those at highest baseline risk of sustaining severe complications and death (e.g. older adults) are least well covered by vaccination, such as is the case in Hong Kong to date.
Variants of concern (VOCs) with higher transmissibility have caused higher proportions of cases and deaths since late 2020. [10,11] Currently, there are limited data on the potential reduction in vaccine effectiveness against VOCs, with some preliminary evidence suggesting that vaccines have a lower effect in preventing mild or moderate infections from VOCs.  Therefore, it is essential that plans for easing restrictions should take into account the ever evolving threat posed by VOCs.
A reduction in the prevalence of other respiratory virus infections (e.g. influenza, RSV) has been observed during the covid-19 pandemic, and this could be attributed to stringent non-pharmaceutical interventions against covid-19. [13,14] In the process of reopening and relaxing public health and social measures, we might expect a resurgence of respiratory viral infections in the upcoming northern hemisphere winter. 
We also recognise the possibility of other difficulties and obstacles in the transition that have not been predicted. Any plans for relaxing restrictions must be evidence-based and we should carefully and deliberately work it out as we work our way back to normality.
Jingyi Xiao is a post-doctoral fellow in the School of Public Health at the University of Hong Kong.
Benjamin J. Cowling is a professor and the division head of the Department of Epidemiology and Biostatistics at the School of Public Health at the University of Hong Kong. Twitter @bencowling88
Gabriel M. Leung is Dean of Medicine and Helen and Francis Zimmern Professor in Population Health at the University of Hong Kong. Twitter @gmleunghku
Competing interests: BJC has consulted for Roche, Sanofi Pasteur, GlaxoSmithKline, AstraZeneca and Moderna.
Funding: BJC is supported by the Senior Research Fellowship Scheme of the Research Grants Council of Hong Kong. BJC and GML are supported by the AIR@innoHK program of the Innovation and Technology Commission of the Hong Kong SAR Government.
Acknowledgments: The authors thank Helen Bond and Jessica Wong for their assistance.
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