The new President of Malawi, Lazarus Chakwera, has told the BBC that his win in the rerun election was a "victory for democracy and justice".
He defeated incumbent Peter Mutharika with 58.57% of votes in Tuesday's poll.
"I do feel like Lazarus, I've come back from the dead," Mr Chakwera said, referring to the biblical character of the same name.
In February, Malawi's constitutional court annulled Mr Mutharika's poll win in May 2019, citing vote tampering.
The country was bitterly divided in the run-up to this week's election. But Mr Chakwera said those who did not support him had nothing to fear.
"There's no cause for fear because I will be your president and my policy for inclusivity means we are building a new Malawi for all of us," Mr Chakwera told the BBC Newshour programme.
"I'm not a president of a faction, I'm a president of everyone in the country," he added.
Mr Chakwera dismissed allegations by Mr Mutharika that the poll was marred by violence and irregularities, saying his predecessor was "misled by rumours".
However, he said he would not stand in the way of Mr Mutharika should he want to challenge the election.
Saulos Chilima, Mr Chakwera's running mate, was also sworn in as vice-president at a ceremony in the capital, Lilongwe.
Mr Chakwera, a Pentecostal preacher and former theology lecturer, said his role would be to unite and serve Malawians.
"I want to provide leadership that makes everybody prosper, that deals decisively with corruption and theft of public funds and a leadership that will follow the rule of law," he told the BBC.
"I do feel like Lazarus, I've come back from the dead, it's been a long journey and we feel vindicated in a way," he said about winning the rerun election.
Other countries in Africa have had elections annulled - it happened in Kenya in 2017 - but for the opposition candidate to then go on and win a rerun is unprecedented.
What did he say in his speech?
"Fellow Malawians, to stand before you as your president today is an honour," Mr Chakwera said in a speech after being sworn in.
He vowed to unite the country and fight poverty.
"Of what use is freedom from oppression if you and I are slaves to starvation? Or freedom from colonialism if you are a slave to tribalism?," he said.
"Time has come for us to go beyond dreaming, time has come for us to wake up, to arise from slumber, and to make our dreams come true," Mr Chakwera said.
"With your help we will restore faith in having a government that serves; not a government that rules, a government that inspires, not a government that infuriates, a government that listens, not a government that shouts but a government that fights for you and not against you," he added.
Mr Mutharika did not attend the ceremony because the law does not require the outgoing president to be present when a successor is taking over, the BBC's Peter Jegwa in Lilongwe reports.
Why was there a new vote?
A rerun of the 2019 election was ordered after the Constitutional Court found the original ballot had been marred by widespread irregularities.
That election saw President Mutharika narrowly re-elected by fewer than 159,000 votes.
Mr Chakwera, who came second in that election, argued that tallying forms had been added up incorrectly and tampered with.
First electionon 21 May 2019
Mutharikasworn in on 27 May 2019
Thousands proteston 20 June 2019, complaining of fraud
Constitutional courtoverturns result on 3 February 2020 and orders re-run
Court rejectsMutharika's appeal on 8 May 2020
Uncertainty around the result sparked months of tension, which spilled over into clashes between opposition supporters and police.
February's annulment led some to celebrate, but Mr Mutharika described it as a "serious subversion of justice" which marked the death of the country's democracy.
There were concerns over the logistics and safety of carrying out an election in the midst of the worldwide coronavirus pandemic.
Who is Lazarus Chakwera?
The opposition leader, a former cleric, heads up the opposition Malawi Congress Party (MCP).
Born in Lilongwe to a subsistence farmer, the philosophy and theology graduate has pledged to raise the national minimum wage, among other reforms.
Candidate for the Tonse Alliance
Born 5 April 1955
Studied theology in Malawi, South Africa and USA
Pastor and lecturer worked at the Assemblies of God School of Theology
Authored several books on religion including Reach the Nations
Ran for president in 2014 and came second
Mr Chakwera leads a nine-party coalition, the Tonse Alliance, and had the backing of former President Joyce Banda as well Mr Chilima, who served as deputy to Mr Mutharika.