Lockdown in Xi’an, China: Delta, Omicron or both?

On Dec. 29, a total of 962 confirmed cases of COVID-19 were reported since Dec. 9 in Xi’an, the capital city of Shaanxi province in northwest China.

The outbreak origin is attributed to several passengers on a plane flight from Pakistan to Xi’an during the first week of December. Initially authorities attributed the outbreak to the Delta variant. Since then, there has been no further mention of how many cases are due to Delta or whether any persons with the Omicron variant have been found during the four mass testing programs carried out this month in Xi’an. In other places in mainland China, fewer than eight cases of Omicron have been reported in travelers arriving from outside China.

Due to community spread in Xi’an, a rising number of daily cases and a few infected travelers from Xi’an to other cities, Xi’an was placed into strict lockdown on Dec. 22.

Before this month, unlike nearly every nation in the world, mainland China has not reported any major outbreaks of the five variants of concern: Alpha, Beta, Gamma, Delta or Omicron. Thus, except for the initial epidemic reported in Wuhan in December 2019, there is almost zero natural immunity to SARS-CoV-2 in the population of mainland China.

COVID-19 vaccines used to fully vaccinate over 1.2 billion people in China have been vaccines made in China, e.g., the two-shot, whole-inactivated Sinovac and Sinopharm vaccines (Beijing and Wuhan), and to a much lesser degree, the one-shot, adenovirus-vectored CanSino Biologics vaccine.  

Given the lack of population immunity among most of the Chinese population (only approximately 101,000 reported infections in all of China since December 2019), and the decreased protection against infection with Delta and Omicron after only two doses of vaccines, preventing spread this winter of Delta and especially Omicron will be a challenge for China and its “zero-COVID” policy. 

The upcoming Chinese New Year (Feb. 1, 2022; the Year of the Tiger) is traditionally accompanied by massive travel beforehand. In addition, the Winter Olympics begin Feb. 3-4.  One can anticipate that China will use its full abilities to prevent these Olympics being linked to Omicron or Delta outbreaks.  

The implications will be global, from virologic to economic, if 2022 and the Year of the Tiger are the first time SARS-CoV-2 spreads extensively in China with risks of creating more novel variants of concern. Let’s hope China can stop even the highly transmissible Omicron.