Research press release


Nature Medicine

COVID-19: Lifting China’s zero-COVID strategy could trigger Omicron wave

もし中国が現在実施中のダイナミック・ゼロコロナ戦略(dynamic zero-COVID strategy)を解除した場合には、オミクロン変異株の大規模な感染拡大が起こって、死者はおよそ155万人、集中治療室(ICU)に対して推定される需要のピークは現在の収容能力の最大で15.6倍に達する可能性がある。これは、Nature Medicine に掲載されるモデル化研究で得られた結果である。


2022年4月18日の時点で、中国では3歳以上の人口の91.4%が規定のスケジュールに沿った重症急性呼吸器症候群コロナウイルス2(SARS-CoV-2)ワクチンの接種をすでに完了しており、さらにその53.7%はブースター接種も受けている。しかしこの免疫だけでは流行を防ぐには不十分かもしれない。2022年3月1日〜4月22日のオミクロン株の新規感染者は50万人を超えており、その93%は上海だが、中国のほぼ全ての省で感染が報告されている。疾病負荷(入院や集中治療が必要な患者数、死者数を含む)をなるべく小さく抑えながら、パンデミックの封じ込めを緩和していくことの実現可能性を検討しようと、H YuたちはSARS-CoV-2伝播の数理モデルを開発し、上海で2022年にオミクロン株流行が最初に急増した段階に合わせて調整を行って、ダイナミック・ゼロコロナ戦略を解除した場合の新型コロナウイルス感染症(COVID-19)の疾病負荷を予測した。



China could see an Omicron wave resulting in approximately 1.55 million deaths and a projected intensive care unit (ICU) peak demand of up to 15.6 times the existing capacity, should its current dynamic zero-COVID strategy be lifted. The findings are published as part of a modeling study in Nature Medicine.

China’s dynamic zero-COVID strategy — which aims at cutting off transmission chains and quickly ending outbreaks — has been in place since August 2021 to respond to SARS-CoV-2 variants with higher levels of transmissibility (such as Delta and Omicron). However, China is now evaluating the sustainability of this policy and potential mitigation strategies.

As of 18 April 2022, 91.4% of the population in China over 3 years of age had received the full schedule of COVID-19 vaccination, and 53.7% of them had received a booster shot. However, this immunity may not be enough to prevent outbreaks. From 1 March to 22 April 2022, more than 500,000 Omicron infections had been reported in almost all provinces across China, with 93% occurring in Shanghai. To explore the possibility of shifting from pandemic containment to mitigation while minimizing disease burden (which includes the number of patients requiring hospitalization and intensive care, and deaths), Hongjie Yu and colleagues developed a mathematical model of SARS-CoV-2 transmission adjusted for the initial growth phase for the 2022 Omicron outbreak in Shanghai to project COVID-19 burden should the dynamic zero-COVID policy be lifted.

In the baseline scenario, which considered a population vaccinated with the booster and an absence of enhanced non-pharmaceutical interventions (NPIs) such as mass testing and mobility restrictions, and antiviral therapies, the emergence of the Omicron variant in March 2022 may have the potential to cause as many as 5.1 million hospital admissions, 2.7 million ICU admissions and 1.55 million deaths within a 6-month period up to September 2022. Unvaccinated people 60 years of age and older are projected to account for 74.7% of the total number of deaths due to the gap in vaccination coverage.

The authors also investigated the impact of three types of strategies to mitigate the COVID-19 burden: promoting further vaccination, including booster doses and promoting vaccination among unvaccinated people 60 years of age and older; antiviral therapies; and enhanced NPIs. None of the assessed individual mitigation strategies alone is enough to reduce the death toll to the level of an influenza season or to prevent exceeding the demand for critical care. However, the authors found that a combination of strategies — including further vaccination of elderly and vulnerable people, providing access to antiviral medication, and NPIs — could reduce the death toll and prevent overwhelming of the healthcare system.

doi: 10.1038/s41591-022-01855-7


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