LHASA -- Southwest China's Tibet autonomous region has been expanding its vaccine coverage to protect people from the raging COVID-19, though it has seen no new cases for more than 21 months.

Tibet has so far administered more than 5.89 million doses of COVID-19 vaccine, compared with its population of 3.65 million, the region's health commission said Saturday.

More than 2.99 million people have received their first shots, roughly 82 percent of the population, while over 2.81 million have gotten the second shots.

The region is also following the rest of the country closely in administering booster shots, and has already completed more than 90,000 third jabs, said the commission.

By the end of Friday, Tibet had reported no new confirmed or suspected case for a streak of 653 days, the commission said in a daily update on COVID-19. The region reported a confirmed case at the end of January 2020, the first and so far only case found in Tibet.

However, success is no reason for complacency. The region has stayed on high alert for the coronavirus and is doing whatever it takes to protect its people.

Last week, the health commission launched the inoculation of the COVID-19 vaccine among children aged 3 to 11, while continuing to widen the coverage of vaccination among those 12 and over.

As usual, the shots are offered to all Chinese residents free of charge.

The move aims to "further raise the coverage of COVID-19 vaccine and form a barrier of herd immunity at the earliest possible date," the commission said.

The region virtually completed the inoculation of people 18 and older at the end of August. In early August, it started the vaccination of those aged 12 to 17.

Facing the resurgence of locally transmitted cases in other parts of China since mid-October, Tibet has notably ratcheted up its control measures. A negative nucleic acid test result is almost routinely required for entry into the region from other provincial-level regions.

Jiang Jie, a vice chairman of the regional government, has ordered "relentless efforts" of regular coronavirus control by fully implementing measures such as temperature checking and sterilization of public areas.

He added local departments must shoulder their due responsibilities to prevent COVID-19 transmission from outside the region, and improve management and control from within.

The national tally showed 57 new locally transmitted COVID-19 cases were reported Friday on the Chinese mainland, bringing the number of total local cases since the middle of October to more than 1,000, scattered across 21 provincial regions.

Over 2.36 billion doses of the COVID-19 vaccine had been administered on the Chinese mainland as of Thursday, according to the National Health Commission.