The main thing is that China is ending its strict zero-Covid strategy. Level of immunity of the population, vaccination… what is the country’s situation with regard to the virus? What development is possible?
China is the only major country that continued to implement a “zero Covid” strategy until recently. She has been rowing back since December 7th. Other countries, including Australia, New Zealand and Singapore, had also attempted to eliminate Covid entirely from their territories early in the pandemic, but all had eventually abandoned that approach. The growing social and economic costs had become unsustainable, as had the efforts required… given the realization that local elimination of Covid could only be temporary.
In the People’s Republic of China, the public health strategy, which relied on measures such as mass PCR testing, the closure of entire cities and provinces, or the quarantine of people who may have been exposed to the virus, has again become unsustainable.
The harshness and often indiscriminate application of zero-Covid has led to growing fatigue and resentment among the population, which has recently led to large public demonstrations.
Limitations have also shown their limitations with Omicron: less severe but more easily transmissible, this variant has a shorter incubation period than previous SARS-CoV-2 lines and largely bypasses the protection against infection of the original vaccines.
It is understandable that the Chinese authorities are finally taking steps to ease restrictions… However, the exit from a zero Covid policy has been painful for all countries that have made it. And China will be no exception, even facing unique challenges in this transition.
Low immunity of the Chinese population
China’s tight control over its population has enabled it to prevent widespread transmission of Covid to its entire (huge) territory since early 2020 – which is a feat. The nearly 10 million cases reported to the World Health Organization over the past three years (numbers vary by source) represent a tiny fraction of its 1.412 billion population. However, this achievement has the unfortunate consequence that exposure to the virus has given the population minimal immunity to Covid.
What about vaccination immunity? The vaccination rates in China are comparable to those in western countries… But they have an unusual characteristic: they decrease with age. Despite being most at risk of severe forms of Covid, the elderly are the least vaccinated demographic, with only 40% of people over 80 having received three doses.
Another point: the effectiveness of vaccines against transmission has been rigorously tested, especially since Omicron began spreading in late 2021. However, protection against the most severe forms and death from vaccines against mRNAs used by Western countries has remained solid.
However, China has used vaccines different from its design, called “inactivated” and manufactured by the companies Sinovac and Sinopharm. This type of vaccine relies on pathogens (in this case SARS-CoV-2, the virus responsible for Covid-19) that are killed or inactivated before being inoculated. While these vaccines are generally safe, they tend to elicit weaker immune responses than newer technologies – such as those used in mRNA (Pfizer and Moderna) or adenoviral vector vaccines (AstraZeneca and Johnson & Johnson).
The performance of Chinese vaccines has therefore been mixed. While two doses of the Sinovac vaccine appear to have reduced deaths by 86% in Chile, the results in Singapore suggest less protection against severe forms than their mRNA equivalents.
Admittedly, the world’s dominant Omicron variant (via its many subvariants) is associated with significantly lower disease severity and mortality rates than the Delta variant it replaced… But it remains a major threat, particularly to populations with low immunity—the elderly .
[Près de 80 000 lecteurs font confiance à la newsletter de The Conversation pour mieux comprendre les grands enjeux du monde. Abonnez-vous aujourd’hui]
The Hong Kong case: a precursor?
In early 2022, Hong Kong faced problems similar to mainland China, as the population had previously had little exposure to the virus. Hong Kong had even lower vaccination rates for the elderly than China currently has, but a stronger healthcare system.
Yet the Omicron wave that swept through the megalopolis in March 2022 resulted in more cumulative deaths per million people in days than many countries have seen throughout the pandemic…
Our World in Data/Johns Hopkins University, CC BY
Covid infections are now increasing rapidly in China, surpassing 30,000 new daily cases in early December (to fall below 9,000 these days due to the end of systematic PCR testing: beware, these numbers are no longer meaningful, people are no longer necessarily communicating the Results of self-tests carried out at home to the authorities, editor’s note). With restrictions easing and the main travel-tracking application shut down, there is no doubt that the rise in infections will continue.
Given the low level of immunity in China, a sharp increase in the number of cases could likely lead to large numbers of hospitalizations and a dramatic number of deaths.
If we assume that 70% of the Chinese population will be infected in the next few months and 0.1% of those infected will die (a conservative estimate of the omicron mortality rate in a population with low exposure to SARS-CoV-2), a simple calculation suggests the death toll could be close to a million. A model from Fundan University (Shanghai) came up with a number of 1.55 million.
At present, there is little China can do to prevent a significant number of cases and deaths. However, any vaccination campaign that focuses on those most at risk is likely still beneficial.
China’s healthcare system is quite fragile and the shortage of intensive care beds represents a particular vulnerability. A gradual lifting of restrictions, as other countries have done, is one option to try to “flatten the curve” and prevent the healthcare system from failing is overwhelmed. Effective patient referral, including ensuring only those most in need of care are hospitalized, could help reduce deaths if the epidemic explodes.
A vulnerable population
A large Covid wave in China will not necessarily have a significant impact on the global situation. SARS-CoV-2 lines currently spreading in the country, such as BF.7 (which is transmitted faster and with a shorter incubation period and greater infectious capacity than other omicron variants; with a number of people infected without transmission Control measures by an infected person or R0 of 10 or more) are already found elsewhere in the world.
Furthermore, circulation in a population with low levels of immunological protection should not place significant additional pressure on the virus to the point that it must evolve new variants in order to spread further.
But for China itself, the situation is different. It could face a possible humanitarian catastrophe, and that’s a much bigger challenge.
The Chinese authorities were the first to take unprecedented measures to stop the spread of the virus and work towards it, providing the planet with a drastic model to deal with the pandemic. China then applied these measures more ruthlessly and longer than any other major country.
In view of the adaptability of SARS-CoV-2, the initially particularly effective zero-Covid policy has proven to be downright “hopeless” in the long run. While its population has been spared more than many and is therefore less immunologically protected, China is now being caught up in the social and economic costs of this strategy. And the virus will continue to spread like everywhere else.
Francois Balloux, Chair Professor, Computational Biology, UCL
This article was republished by The Conversation under a Creative Commons license. Read the original article.