Shanghai’s Response to Fast Spreading of the COVID-19 Pandemic-Omicron (B.2)

Introduction

On November 9, 2021, South Africa identified a new variant of the novel coronavirus B.1.1529.¹ On November 26, the World Health Organization designated B.1.1.529 as a variant named Omicron, following Alpha, Beta, and Delta variants, which has replaced Delta as the world’s predominant variant.² There are five Omicron subvariants: BA.1, BA.2, BA.3, BA.4, and BA.5, of which the BA.2 subvariant was the main strain that triggered the COVID-19 outbreak in Shanghai.

The first case of an Omicron variant in China was reported by Sun et al.³ Prior to March 1, 2022, cases attributed to Omicron in Shanghai were sporadic, and the overall pandemic prevention and control were good. Since March 1, more than 649 655 cases of infections have been reported in this wave of epidemics. Besides, from March 1 to June 30, asymptomatic cases accounted for 91.05% of the total number of confirmed and asymptomatic cases (591 518/649 655). Among all the patients, 62 931 were cured and 595 dead. Confirmed and asymptomatic cases in Shanghai are shown in Figure 1.

Figure 1.

Number of confirmed and asymptomatic cases in Shanghai from March 1 to June 30.

Why Is Omicron Highly Transmissible But Less Severe?

It is because Omicron owns (1) strong immune evasion capability. There are many mutations at amino acid residues in the virus spike protein (S). More than 30 mutations are found in the S protein of the BA.1 subvariant, which is the target antigen for vaccines. Therefore, it has strong potential to evade neutralizing antibodies induced by infection or vaccination.⁴ (2) It has strong infectivity. The S protein mutation enhances the virus-binding affinity of the receptor and its ability to invade respiratory epithelial cells.⁵

In terms of hospitalization and mortality rates, Omicron has milder symptoms than other variants, and most patients are mild or asymptomatic.⁶ Veneti et al⁷ combined the hospitalization rates of 39 524 Omicron cases and 51 481 Delta cases and found that the former reduced the risk of hospitalization by 73%. This is mainly because the Omicron variant primarily invades the upper respiratory tract, and not the lower respiratory tract, and most people are vaccinated or have a certain degree of immunity from previous infections.

How Are Close and Secondary Contacts of Confirmed Cases Determined in Shanghai?

The key to breaking the transmission chain of COVID-19 and curbing the pandemic lies in the rapid and accurate identification of close and secondary contacts during the early stages of the outbreak.⁸ Close contacts are people who have had close contact with a suspected or confirmed case without effective protection from two days before the onset of symptoms or two days before the sampling of an asymptomatic infection specimen. Currently, close contacts in Shanghai are required to be quarantined in a quarantine facility for 14 days, followed by seven days of self-health management, during which seven nucleic acid tests will be performed.

Meanwhile, secondary contacts are those who have had close contact with a close contact without effective protection (eg, living under the same roof, working in the same enclosed environment, and eating or just spending time together). Secondary contacts must be quarantined for seven days either in a quarantine facility or at home, followed by seven days of self-health management, during which five nucleic acid tests will be performed.

What Are the Current Pandemic Prevention and Control Measures in Shanghai?

Shanghai has adopted a grid-based approach to expand screening coverage and curb the spread of the virus. In locked-down areas, people are required to stay at home and public transportation is suspended, further reducing the flow of people and breaking the transmission chain. The specific measures are as follows:

1. Residential communities/neighborhoods with newly reported confirmed cases were designated as locked-down areas. Residents were required to stay at home using door-to-door services. Residential buildings with confirmed cases will be locked down for 14 days, whereas other buildings in the areas will be locked down for seven days, followed by another seven days of community-based health management with additional testing. Some citizens have suffered from inconveniences of lockdown in their daily lives. However, social workers and volunteers have made great effort to the care of those people in need from both material and psychological perspectives.

2. Other areas in the subdistricts and towns with newly reported confirmed cases were designated as managed and controlled areas. Residents are required to stay within the community for seven days under community-based health management with additional testing, and gatherings are strictly prohibited. In principle, one resident from each household was allowed to collect distributed materials from designated areas in the community. This will be staggered with neighbors to ensure that it is a contactless trip.

3. Areas that are not locked down, managed, or controlled are designated as precautionary areas. Residents in this area should avoid going out and reducing the flow of people and gatherings. They were encouraged to stay at home and work. If they need to leave, they should take appropriate personal protection measures and maintain social distancing. They must avoid going to crowded places and adhere to measures such as body temperature measurement. If they show symptoms, such as fever, dry cough, fatigue, sore throat, hyposmia, and diarrhea, they should seek medical treatment at the nearest medical institution in a timely and proactive manner.

Why Can’t China “Coexist With COVID-19” In Terms of Pandemic Prevention and Control?

China’s pandemic prevention and control measures emphasize “People First, Life First.” Since the outbreak of the COVID-19 pandemic, China has been insisting on a dynamic zero-COVID approach and continuously optimizing prevention and control measures to protect citizens from the virus through natural infection, also known as herd immunity.⁹ In Shanghai, with a population of 25 million, the overall vaccination coverage exceeds 90%; however, vaccination coverage has remained low in older adults—62% of 5.8 million people older than 60 years have been vaccinated, and only 38% have received a booster vaccination.¹⁰ Therefore, it is best option for us to adhere to the dynamic zero-COVID policy at this stage.

Conclusion

The government must be better prepared, listen to experts’ opinions, and respond accordingly. We should continue to wear masks, vaccinate, and develop new vaccines. It should not be expected that the pathogenicity of the novel coronavirus will continue to weaken as it mutates and that the immunity generated by the breakthrough infection of Omicron will be less powerful and short-lived. Therefore, currently, there is no basis for the theory that Omicron will be the end of the COVID-19 pandemic.