China has shortened the COVID-19 quarantine time for inbound international travelers and refined the designation of medium- and high-risk areas, in an effort to cope with the highly infectious Omicron variant more precisely, according to a document released on Tuesday.

"The adjustment by no means suggests a loosening of novel coronavirus control measures. Rather, we are aiming for higher standards and more targeted and faster response in dealing with outbreaks, while adhering to the dynamic zero COVID-19 strategy," said Lei Zhenglong, deputy director of the National Health Commission's Bureau of Disease Prevention and Control, during a news conference.

The State Council's Joint Prevention and Control Mechanism released the ninth and latest prevention and control guideline for COVID-19 on Tuesday, more than a year after the previous version was published.

According to the document, inbound travelers only need to undergo centralized isolation for seven days, rather than 14 days under the previous rule, and then spend three days in self-quarantine at home. The rule also applies to close contacts of confirmed COVID-19 patients.

People who in turn are close contacts of the close contacts of COVID-infected people will go through seven days of isolation at home rather than in centralized quarantine, it added.

Wang Liping, a researcher at the Chinese Center for Disease Control and Prevention, said cutting quarantine time should not be interpreted as a relaxation of precautions.

"The dominant strain in China and abroad is Omicron, and research shows that the incubation period of Omicron is around two to four days, shorter than earlier strains. Most positive cases can be confirmed within a week." She said. "The policy shift is aimed at upgrading virus control measures based on the variant's characteristics without increasing the risk of the virus' spread. The change reflects the principle of precise disease control."

The guideline also formulates new standards for listing areas deemed at risk of the virus' spread.

The designation of high-risk area usually refers to the residence of confirmed infections and can only cover a certain residential compound. People living there are required to stay at home.

Medium-risk refers to places where confirmed infected patients have visited and stayed for some time. Such an area's perimeter should be decided based on epidemiological results, instead of the previous convention of listing a whole neighborhood or village. People there are not allowed to travel outside the area.

The remaining areas in a district or county that has at least one medium- or high-risk area will be listed as low risk. When people living there travel outside, they should present negative nucleic acid test results taken within 48 hours and complete two tests in three days at their destinations.

The new rule is also flexible. "If new infections are sporadic and the virus deemed at low risk of spreading, local authorities are allowed to skip risk designations," said Lei.

The updates come as China has brought under control a recent wave of domestic outbreaks that hit metropolises and border towns particularly hard.

"The stabilizing epidemic situation has created a window of opportunity for us to adjust the guideline," Lei said, adding that trial programs were launched in seven cities in April and May to add science-based evidence to the revision.