Modeling transmission of SARS-CoV-2 Omicron in China

Abstract

Having adopted a dynamic zero-COVID strategy to respond to SARS-CoV-2 variants with higher transmissibility since August 2021, China is now considering whether, and for how long, this policy can remain in place. The debate has thus shifted towards the identification of mitigation strategies for minimizing disruption to the healthcare system in the case of a nationwide epidemic. To this aim, we developed an age-structured stochastic compartmental susceptible-latent-infectious-removed-susceptible model of SARS-CoV-2 transmission calibrated on the initial growth phase for the 2022 Omicron outbreak in Shanghai, to project COVID-19 burden (that is, number of cases, patients requiring hospitalization and intensive care, and deaths) under hypothetical mitigation scenarios. The model also considers age-specific vaccine coverage data, vaccine efficacy against different clinical endpoints, waning of immunity, different antiviral therapies and nonpharmaceutical interventions. We find that the level of immunity induced by the March 2022 vaccination campaign would be insufficient to prevent an Omicron wave that would result in exceeding critical care capacity with a projected intensive care unit peak demand of 15.6 times the existing capacity and causing approximately 1.55 million deaths. However, we also estimate that protecting vulnerable individuals by ensuring accessibility to vaccines and antiviral therapies, and maintaining implementation of nonpharmaceutical interventions could be sufficient to prevent overwhelming the healthcare system, suggesting that these factors should be points of emphasis in future mitigation policies.

Assessing the feasibility of sustaining SARS-CoV-2 local containment in China in the era of highly transmissible variants

“…These estimates were also in agreement with the projections of Cai et. al., based on the projections of dynamical models 14 . Given that SASR-CoV-2 has been continuously undergoing rapid adaptive evolution 19 , we further consider a hypothetical SARS-CoV-2 variant with 50% increase in disease severity and another one with increased immune evasive properties comparing to Omicron BA.2 (detailed description in Supplementary Table 2).…”

Covid-19: WHO chief calls for a shift in China’s “unsustainable” policy

“…If China is to move away from its zero covid policy it should gradually reduce restrictions and focus on protecting the most vulnerable, said authors of a study published in Nature Medicine 9…”

The Origin of Immunity by Means of Prior Infection and Vaccination with Implications for the Origin of Species

“…After the last surge in the incidence of COVID-19 cases, which was attributed, through logical deductions from data, to the appearance of the Omicron variant surge, daily cases began to decline in the United States and globally to their lowest levels in over 6 months but in May 2022, the reported number of cases began rising again. 1,2 And this surge is being attributed, again through logical deductions from data, to the emergence of Omicron's sub variants, progressive waning of the immunity obtained by means of prior infection and vaccination 1,3,4 as well as the lifting of mandates such as mask use and other restriction aimed at reducing transmission. 1 Given the fact that the mechanisms by which vaccines protect us against pathological manifestations that appear in response to pathogens are so poorly understood that it has been impossible to develop vaccines that are effective against major killers of humankind, from ancient Tuberculosis and malaria to old HIV/AIDS, 5,6 and that the development of effective vaccines to control outbreaks of pathological manifestations that have the capacity to threaten global health security such as Ebola and COVID-19 is currently facing challenges, an understanding of the immunological basis for vaccination has been considered urgently needed.…”