Vietnam’s most-powerful official, General Secretary Nguyen Phu Trong who heads the communist party, has stepped aside indefinitely due to health reasons, according to a government statement.

President To Lam, Trong’s long-time anti-corruption crusader who was appointed in May, will become the interim leader, the statement Thursday said.

Trong, 80, who is in his third term as party chief, “had been working while being under health treatment in recent time,” the statement said. “The Politburo and other top leaders have directly ordered specialized agencies to mobilize leading doctors, medical staff and to provide most favorable conditions for treatment and health care for the party chief.”

Trong’s failing health has added to the political uncertainty that has gripped the nation’s leadership amid a wide-spread anti-corruption campaign spearheaded by the party secretary. The so-called “blazing furnace” drive last year ensnared at least 459 Communist Party members, as well as business executives. 

Lam, the former minister of public security, became the country’s third president in less than two years after his two immediate predecessors resigned for “violations” that were possibly detected by the ministry that Lam oversaw.

Trong’s health has been the topic of speculation for years, and one he’s addressed himself. He appeared reluctant to take the top job when he was re-elected for a third term in 2021, saying at the time he preferred to retire because, “I’m old and not in good health.” Trong was hospitalized in January because of an unspecified illness.

“We’ve never seen a sudden change like this in the party and it shows Trong’s health problem is very critical,” said Le Dang Doanh, an economist and former government adviser in Hanoi. “This move is to get everyone well prepared for the next step.”

The latest development puts Lam, who as president is the second-highest ranking official within the party’s political hierarchy, in a strong position to become the next party chief, but it’s not guaranteed, said Carl Thayer, emeritus professor at the University of New South Wales in Australia.

For now, “To Lam will assume the role of caretaker,” Thayer said. 

In addition to Lam, candidates for the next party chief could be Prime Minister Pham Minh Chinh, National Assembly Chairman Tran Thanh Man and Tran Cam Tu, chairman of the Central Inspection Committee, because all have met the requirement of serving at least one term in the Politburo, Thayer said. The indefinite absence of Trong gives the party time to develop “a consensus of whether To Lam should be the candidate or someone new,” he said.

The posting on the government website tried to reassure that the one-party system can manage the country during Trong’s health emergency. “The Politburo calls on the entire party, the people and the army to have an absolute trust in the party’s leadership and the state management,” it said.

While the latest turn of events in Vietnam’s politics — with Trong stepping down due to health issues — is “unprecedented,” said Thayer, “they are following the script embedded in the party’s rules and regulations.”

The Politburo awarded Trong with the Gold Star Medal, the nation’s highest honor, for his contributions to the party and the nation, the government said in another statement Thursday.