New Caledonia's authorities are concerned about the quick propagation of the Omicron variant of Covid-19 which was first detected earlier this month.
More than 300 new cases have lately been recorded every day, with the seven-day average now up to 200 cases.
76 percent of those 12 years and older have had two jabs since vaccinations started exactly a year ago, but about a fifth of the population has declined to be inoculated.
In September, Congress passed a law making vaccinations mandatory, but its application has been repeatedly deferred and is now expected to be enforced before the end of February.
The move made New Caledonia the fourth country to impose vaccination compulsion, after Tajikistan, Turkmenistan and the Vatican.
Frontline staff and healthcare employees are being threatened with fines, but there is no provision to sanction the general public.
When the law was drawn up, New Caledonia was Covid-19 free but within days the Delta variant was detected, triggering a state of emergency and a month-long lockdown.
More than 280 people died in the outbreak.
The use of a health pass has been mandated since the end of the lockdown in October in order to be able to enter venues.
The vaccination law as well as other restrictions have been criticised by civil society groups, with several demonstrations being held in Noumea in defiance of the meeting rules.
A spokesperson of the group ReinfoCovid NC, Gaelle Wery, was detained after last weekend's rally, which had been explicitly forbidden by the French High Commission.
Hundreds of people had taken part in the gathering despite there being a limit of 30 people for any outside meeting.
Photo: 123RF
She was set free but is to appear in the criminal court in May over her role in the event.
In a separate development, a formal complaint has been lodged against the president Louis Mapou and the Congress president Roch Wamytan for allegedly endangering a person's life.
A representative for a 19-year-old woman at the centre of the case said she suffered partial paralysis after her vaccination.
According to the public broadcaster, the complaint said vaccinations were made mandatory without there being a compensation scheme.