Health officials have called for "swifter" and "more targeted" efforts to enforce the 20 optimization measures of the COVID-19 containment policy released last week as China finds itself tacking a surge of Omicron-fueled cases.

Previously, China traced and isolated not only "close contacts" of confirmed cases, but also those secondary contacts with close contacts. In addition, places used to be labeled as low-, medium- or high-risk areas in the previous three-tier system based on infection hazards.

However, the "secondary close contacts" will no longer be designated or quarantined under the new rules, and the "medium-risk region" label has been retired. Furthermore, high-risk places are now designated as smaller areas such as residential buildings rather than entire communities or districts.

Shen Hongbing, director of the National Disease Prevention and Control Bureau, said the change helps make the most of epidemic control resources such as contact tracing and isolation venues.

Some places tend to overly enforce the rules and had managed the less risky group as if they were close contacts, which is "unnecessary", he told a news conference on Thursday.

But Shen, also academician at Chinese Academy of Engineering, suggested that dropping the category does not make the control effort any easier. Instead, contact tracers need to move more quickly to locate and test close contacts.

"Once the close contacts test positive, they need to quickly trace their own close contacts," Shen said.

Wang Liping, a researcher with Chinese Center for Disease Control and Prevention, said: "The designation of medium-risk places would put a sizable population under restriction, but the positive rate is rather low."

With the label gone, control work needs to be more accurate and efficient, she said.

The new rules came as China works to curb oversimplicity in enforcing epidemic control measures and reduce their impact on people's lives.

Shen said the COVID-related complaints dropped 39 percent less than a week after the new rules were unveiled.

Among the complaints, one-fourth were about returnees from low-risk regions being told not to return or placed under isolation. Others centered on randomly enlarging the scale of restriction measures.