Prime Minister Robert Abela and his family are in quarantine after Lydia Abela tested positive for COVID-19 - on the day she received her first dose of the vaccine.
The prime minister said in a Facebook post that his wife had taken a test in view of engagements in the coming days and the result was positive.
"Lydia is well and has not had any symptoms," the prime minister said, adding that he and their daughter Giorgia Mae tested negative.
"This naturally means that we have started to observe a period of quarantine," Abela said.
He said he would continue to work from home, using technology to take part in important meetings scheduled for the next few days.
Abela was expected in Portugal this weekend, to take part in the European Council's Porto Social Summit.
The prime minister himself took the first dose of the vaccine earlier this week.
30 new cases of COVID-19 were reported on Wednesday.