People not vaccinated against Covid-19 are no longer allowed in restaurants, bars, tourist sites and gyms in France unless they have recently recovered from the virus.
The new law came into force on Monday, requiring a “vaccine pass” which is central to the government’s anti-virus strategy.
France has the highest daily number of coronavirus infections on record in Europe, and hospitals continue to fill with Covid patients, although the number of people in intensive care units has fallen in recent days.
The government imposed few other restrictions amid the surge in the Omicron variant, focusing instead on the vaccine pass, approved by Parliament and the French Constitutional Council last week.
Omicron is less likely to cause severe disease than the previous Delta variant, studies show.
It spreads even more easily than other strains of coronavirus and has already become dominant in many countries.
Omicron also more easily infects people who have been vaccinated or who have already been infected with earlier versions of the virus.
Critics question whether the pass will make much of a difference in a country where 94% of French adults have received at least one dose of the vaccine, and scattered groups staged protests against the new law on Saturday.
The government hopes to protect the most vulnerable and reduce pressure on crowded intensive care units, where most patients are unvaccinated.
Since last summer, France has required a “health pass” to go to any café, museum, cinema or take a regional train or domestic flight.
But until Monday, unvaccinated people could activate the pass by getting a recent negative test.
The new pass only works for people who are fully vaccinated and those who have recently recovered from the virus.
France, meanwhile, opened access to reminders to 12-17 year olds on Monday.