President To Lam would take over as the country’s caretaker leader, the party said in an online statement.
The party said Lam had been assigned to lead the works of the party central committee, the politburo, the secretariat, while Trong would “focus on active treatment”.
Led by the Communist Party general secretary, Vietnam’s leadership structure gives the president the second-most authority — but the position is largely seen as ceremonial.
The communist government’s four-person hierarchy also includes the prime minister and the head of the National Assembly.
Trong’s ailing health has fuelled widespread speculation that he will not be able to stay in power until the 2026 party congress that is expected to appoint a successor.
In office since 2011, the party leader has enjoyed remarkable longevity in his role, which rights groups say has coincided with Vietnam’s drift toward authoritarianism.
Lam, 67, served as Vietnam’s public security minister before being voted in as president by Vietnam’s rubber-stamp parliament after a major anti-corruption campaign forced his predecessor to resign.
Thousands of people — including several senior government and business leaders — have been caught up in the Southeast Asian country’s crackdown on graft, led by Trong.
Analysts have said that Lam, who is deputy head of the steering committee on anti-corruption, has weaponised its investigations to take down his political rivals.
In his first remarks as president, Lam said he was “determined to fight corruption and negative phenomena”.
