It is perplexing why China chose to lift zero-COVID policy and do away with the strict NPIs, in winter, just before the Chinese New Year, when a highly transmissible subvariant BF.7 was already in circulation.
“WHO is very concerned over the evolving situation in China,” WHO Director-General said on Wednesday (20th December 2022) on high surge in COVID cases in China.
While rest of the world reeled under the pandemic, China had relatively low infection rate due to continuous adoption of zero-COVID policy through strict implementation of nonpharmaceutical interventions (NPIs). Nonpharmaceutical Interventions or community mitigation measures are public health tools like physical distancing, self-isolation, limiting the size of gatherings, school closure, working from home, etc that help in preventing and controlling spread of disease in the community. Strict NPIs severely restricted people -to-people interaction that satisfactorily limited transmission rates of the virus and managed to keep number of deaths to the lowest. At the same time, near-zero interaction was also not conducive to development of natural herd immunity.
Along with strict NPIs, China had also undertaken massive COVID-19 vaccination (using Sinovac or CoronaVac which is a whole inactivated virus vaccine.) that saw about 92% people receiving at least one dose. The figure for elderly people of 80+ age group (who are more vulnerable), however, was less satisfactory at 77% (received at least one dose), 66% (received 2nd dose), and 41% (received booster dose as well).
In the absence of herd immunity people were left solely on vaccine induced active immunity which may have been either less effective against any new variant and/or, with time, the vaccine induced immunity may have tapered off. This along with unsatisfactory booster vaccine coverage meant relatively low levels on immunity among the people in China.
It is in this background, China lifted strict zero-COVID policy in December 2022. Popular protests may have been partly responsible for the switch from “dynamic zero tolerance” (DZT) to “totally no inventions” (TNI).
The easing of restrictions, however, has resulted in massive surge in cases. Unverified reports emanating from China indicates much larger number of mortalities and overwhelming of hospitals and funeral care institutions than reported officially. The overall global figure crossed half a million daily average cases mark in week ending 19th Dec, 2022. Some hypothesise that the current spurt could well be the first of the three winter waves, linked to mass travels before and after Chinese New Year celebrations on 22 January 2023 (a pattern reminiscent of the early phase of COVID-19 pandemic seen in 2019-2020).
It seems, BF.7, the omicron subvariant associated with surge of COVID-19 cases in China is highly transmissible. Effective reproduction number for this subvariant in Beijing during November -December 2022 was estimated to be as high as 3.421.
The COVID-19 scenario for China in near future appears to be challenging. According to a model based on the recent pandemic data of Macau, Hong Kong, and Singapore, 1.49 million deaths are predicted in China within 180 days. If relaxed nonpharmaceutical interventions (NPIs) are adopted after the initial outbreak, the number of deaths could be brought down by 36.91% within 360 days This is called “flatten-the-curve” (FTC) approach. Complete vaccination and use of anti-COVID drugs can reduce the number of deaths among elderly (60 years plus) age group to 0.40 million (from projected 0.81 million)2.
Another modelling study projects less severe scenario – between 268,300 to 398,700 deaths, and peak numbers of severe cases between 3.2 to 6.4 per 10,000 population before the wave recedes by February 2023. Enforcement of weak NPIs may reduce number of deaths by 8% while strict NPIs may reduce deaths by 30% (compared to totally no interventions). Fast booster dose coverage and strict NPIs would help improve scenario3.
It is perplexing why China chose to lift zero-COVID policy and do away with the strict NPIs, in winter, just before Chinese New Year, when a highly transmissible subvariant BF.7 was already in circulation.
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References:
- Leung K., et al., 2022. Estimating the transmission dynamics of Omicron in Beijing, November to December 2022. Preprint medRxiv. Posted December 16, 2022. DOI: https://doi.org/10.1101/2022.12.15.22283522
- Sun J., Li Y., Shao N., and Liu M., 2022. Is it possible to flatten-the-curve after the initial outbreak of Covid-19? A data-driven modeling analysis for Omicron pandemic in China. Preprint medRxiv . Posted December 22, 2022. DOI: https://doi.org/10.1101/2022.12.21.22283786
- Song F., and Bachmann M.O., 2022. Modelling of outbreaks of SARS-CoV-2 Omicron variants after easing Dynamic Zero-COVID strategy in mainland China. Preprint medRxiv. Posted December 22, 2022. DOI: https://doi.org/10.1101/2022.12.22.22283841
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