China’s move to lift Covid-19 restrictions has been abrupt and far more swiftly implemented than expected, prompting other countries to impose travel restrictions on its citizens. Clinical virologist Siddharth Sridhar of The University of Hong Kong reckons that the immediate priorities for the country, which accounts for a fifth of the world’s population, are clear – urgently increase vaccination rates, boost critical care infrastructure, and improve the distribution of antivirals – but this path will be onerous in the short term.
Covid patients in a Shanghai hospital, January 3: The immediate priorities are clear – urgently increase vaccination rates, boost critical care infrastructure, and improve the distribution of antivirals (Credit: Chinatopix)
In these first weeks of 2023, the world seems to be going through a collective déjà vu of events in early 2020, when the pandemic was just unfolding. Like then, there is once again a major outbreak of Covid-19 in mainland China. Once again, many countries are imposing travel restrictions on Chinese travelers. And once again, fears of new Omicron super variants are circulating widely in social and mainstream media.
These superficial similarities aside, what does the Omicron outbreak in China mean for the region and the world?
The culminant iteration of viral evolution in 2021 was Omicron, a variant so different from its predecessors that it sparked off large waves around the world including Hong Kong. Omicron enjoyed widespread circulation globally through most of 2022 in the form of its sequential subvariants: BA.1, BA.2, and BA.4/BA.5. Of late, Omicron has splintered into myriads of subvariants vying for global dominance. The most “successful” (e.g., BA.2.75.2, XBB.1.5, BQ.1.1) share a common attribute in that they are increasingly able to evade antibodies generated from previous Omicron infections or first-generation vaccines.
The silver lining is that Omicron infections are often mild due to a combination of inherently reduced transmissibility and prior immunological experience in infected patients. Therefore, in places with high levels of hybrid immunity (arising from combinations of infections and vaccinations), Covid-19’s toll on public health is much diminished when compared to the nadir of the pandemic. Updated bivalent mRNA vaccine boosters encoding BA.4/BA.5 are further bolstering immunity in individuals most at risk of severe disease, i.e., the elderly and those with chronic medical conditions. Availability of antivirals for early infection can further relieve pressure on healthcare systems during large waves of Omicron. Humanity has developed tools to live effectively with Covid-19, which itself is well adapted to us and will continue to circulate as another seasonal respiratory virus.
The situation in mainland China, however, sharply contrasts with that of the rest of the world. China had adhered to a strict zero-Covid policy for the best part of the last three years. This policy relied on strict border controls, centralized isolation and quarantine, mass testing, surveillance, and a low threshold for lockdowns to contain Covid-19 at very low levels even as other parts of the world were being engulfed by sequential waves.
Zero Covid, however, was obviously going to be difficult to sustain in the age of Omicron. This struggle was exemplified by the protracted Shanghai outbreak from February to August last year. Difficulties notwithstanding, it was always clear why China was sticking to zero Covid from a public health perspective. Due to a number of factors, uptake rates of vaccines by elderly in China are suboptimal, particularly those for the third (booster) dose, which is important when the primary course is an inactivated vaccine.
Hybrid immunity was non-existent in China as most of the vast population had never contracted Covid-19. Oral antivirals for treating early Covid-19 were not widely available. Critical care beds are limited and unequally distributed across the vast country. With this background, the consequences of dropping zero Covid, especially during winter which sees accelerated virus transmission, appeared a foregone conclusion.
And then, almost overnight, zero Covid became a thing of the past.
On January 8, China reopened its borders and removed quarantine restrictions. Hard numbers are difficult to come by, but the high proportion of Chinese travelers testing positive for Covid-19 at overseas ports is compelling evidence of the extent of the current Chinese outbreak. Hospitals are coming under pressure in scenes reminiscent of the early months of the pandemic. With China accounting for a fifth of the world’s population, it is likely that its current outbreak will last into early 2023 with resurgent smaller waves burning through the uninfected population. The exact death count will be difficult to gauge due to differences in how Covid-19 mortality is measured, but comparisons with average all-cause mortality figures in past years will eventually yield an accurate picture of the toll of this outbreak. This is not just about Covid-19: In Hong Kong and elsewhere, paralysis of the healthcare system by cases of the coronavirus also contributed to considerable mortality in patients with non-Covid emergencies unable to access timely medical attention.
While this is a difficult time for its citizens, China is now officially open. The world has had mixed reactions to this. Several governments have imposed pre-travel testing requirements on travelers from the country, with some including Hong Kong and Macau. Their justification for this measure is the concern of new dangerous variants emerging from unchecked transmission in the region.
So far, however, there is no evidence that this is happening. Data submitted to the World Health Organization (WHO) by Chinese scientists only indicate circulation of well-known Omicron subvariants such as BF.7 and BA.5.2. These are relatively “old” subvariants found in pockets worldwide since mid-2022. Indeed, these subvariants are being ousted by fitter rivals such as BQ.1.1 and XBB.1.5 in many parts of the world. This highlights the fact that evolutionary pressures on the virus in mainland China are different to the rest of the world for the moment. In the mainland, the circulating virus is facing little immunological pressure in an overwhelmingly infection-naïve population, whereas overcoming high levels of hybrid immunity by antibody evasion is a prerequisite for a successful subvariant in the rest of the world.
Predicting viral evolution is fraught with uncertainty, but it at least appears that the short-term emergence of a new “supervariant” in the mainland is by no means a fait accompli. Of course, ongoing genomic surveillance is key as stressed by the WHO. In addition to local surveillance, the opening of the Chinese border means that such monitoring will be conducted globally in infected travelers coming down with Covid. Even in the event of a new subvariant gaining a global foothold and causing mass reinfections, hybrid immunity will weaken the link between case counts and severe disease rates. Continuing to promote booster vaccinations for the elderly, immunocompromised and those with pre-existing medical conditions remains as essential as ever. In any case, the experience of Omicron’s emergence in late 2021 makes it abundantly clear that performative unilateral travel restrictions will do nothing to halt dissemination of new Covid-19 variants.
The immediate priorities for China are clear – increase vaccination rates urgently, boost critical care infrastructure, and improve antiviral distribution pipelines. The way forward, however, will be difficult. Yet, as the final fifth of the global population begins co-existing with Covid-19, the world is truly collectively moving into the post-pandemic era.
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Reyes, Alejandro. (July 15, 2022) “Roaming in the Wild: Lessons from a Journey in the Post-Covid World”, AsiaGlobal Online, Asia Global Institute, The University of Hong Kong.
The University of Hong Kong