Covid-19: What can China learn from Hong Kong and Singapore about exiting zero covid?

China’s “zero covid” strategy was successful in protecting the Chinese population throughout the first phase of the covid-19 pandemic. However, following widespread recent protests in Beijing, Shanghai, and elsewhere, ostensibly triggered by a fatal fire in Urumqi and aggravated by pictures of maskless fans at the football World Cup, the Chinese government announced that most of its covid restrictions would be relaxed. As Mainland China retreats from its zero covid policies what lessons can China take from the management of covid-19 in Hong Kong and Singapore?

There is good evidence that before the availability of vaccines, elimination was the most effective pandemic strategy.1 In Hong Kong, this strategy, based upon test, trace, and isolate, meant that by the time vaccines were rolled out, the city of 7.4 million people had a cumulative population covid-19 mortality of 26 per million.2 At that time, a Hong Kong resident was 68 times less likely to have died of covid-19 than a resident of the UK.[2]

Once vaccines were widely available, it was clear that the optimal strategy was to achieve high levels of vaccination starting from the most vulnerable down to the rest of the population. By the beginning of 2021, Hong Kong had excellent access to vaccines, provided free of charge in highly efficient temporary vaccination centres. However, when the omicron wave hit in early 2022, only 23% of those aged over 80 years were fully vaccinated. The impact of the omicron wave on this under protected population was devastating.3 The health system was overloaded, and Hong Kong had the highest per capita covid-19 mortality rate in the world in early 2022.

The comparison with Singapore provides valuable lessons. Hong Kong and Singapore pursued similar strategies early on in the pandemic and both had early access to vaccines. Singapore prioritised mRNA vaccines, focused on early vaccination of the most vulnerable, and developed a clear and well communicated plan. This plan included messaging to prepare the population, followed by a graduated reduction in mitigation resulting in a transition from “zero covid” over a period of 6-12 months.4 Singapore has now removed most restrictions and currently has a cumulative covid-19 mortality of 303 per million, compared to 1463 per million in Hong Kong, which continues to have restrictive social distancing policies.5

The high mortality rate in Hong Kong was a direct result of two factors: a failure to vaccinate those most vulnerable and an overloading of the health system. Both factors were influenced by a politicisation of the public health response, which failed to adapt to evolving evidence and generally ignored the advice of public health experts, in favour of second guessing what may be perceived as politically acceptable to China.6 While Singapore communicated a clear plan for transition, both messaging and policy in Hong Kong continued to focus on the strategy of elimination. Vaccine hesitancy among the city’s older adults was impacted by cultural factors including beliefs about Western medicines, fear of side effects of new vaccines, and perceptions of ageing. But the most important factor in low vaccine uptake in the vulnerable was a lack of perceived benefit.7 The focus on the illusion of permanent zero covid in addition to an exaggerated confidence in non-pharmacological interventions, especially masking, led to “rational” vaccine hesitancy.

China has a very large population, and while health systems in urban centres are rapidly evolving, it is unclear to what extent these systems, and even more so those in rural areas, could withstand the impact of a huge surge in demand. In this context, elimination was a valid strategy for China until high levels of vaccination, drug procurement, and preparation of the health system had been achieved. China built enormous capacity in all areas of testing, tracing, and isolation, facilitated by community organisations at a district level and widespread use of digital and surveillance technology to identify potential contacts and impose rapid and high volume lockdowns. Recent reports suggested that 76.6% of those over 80 in China have received two doses of one of the domestically produced inactivated whole virus vaccines, and 65.8% have had three doses. Evidence from Hong Kong suggests these vaccines are >98% effective against death and severe disease, but only after three doses.8 Until very recently, the political narrative within China was that “dynamic zero covid” was for the long term and not a transitional strategy. The continued focus on the messaging of elimination means that, notwithstanding higher vaccination rates in the most vulnerable, China is closer in terms of preparation for transition out of “dynamic zero covid” to Hong Kong than to Singapore.

Getting enough of the older population vaccinated to transition to managed endemicity will take time. PCR positivity rates in addition to reports from major Chinese cities suggest that case numbers are already rising rapidly and health systems are under significant stress. The rapid pivot away from zero covid has understandably resulted in confused messaging. Most worryingly there appears to be no coordinated transitional plan for ongoing mitigation. During the deadly BA.2 wave in Hong Kong in early 2022, mask mandates and social distancing measures in place at that time, meant that the doubling time of the pandemic in Hong Kong was 3.1 days rather than 2 days internationally.9 Even with this degree of mitigation the hospital system crashed. It is likely that the mortality rate would have been even higher in the absence of mitigation.

There are many lessons to learn from the different strategies employed internationally during the pandemic. The differential mortality rates between Hong Kong and Singapore provide a stark contrast between the strategies of zero covid with and zero covid without an exit plan. The lesson from Singapore is that it is possible to transition from elimination to living with covid-19, but that this demands high rates of vaccination and a well communicated transitional plan with a graduated reduction in mitigation over time. The lesson from Hong Kong is that failure to acknowledge and communicate the need for such a transitional plan can be devastating for population health.