Some 5000 people take part in a demonstration to protest against the health pass and measures aimed at curbing the spread of the Covid-19 on January 9, 2022 in Brussels. AFP
There was no repeat of the violence that had marred previous, larger demonstrations in the Belgian capital, although police intervened to surround a small group that approached the EU headquarters.
As it marched through the city the crowd -- 5,000-strong according to the police -- chanted "freedom, freedom!" and brandished banners denouncing what they called a "vaccine dictatorship".
Before the march began, police detained 11 suspects found to be carrying fireworks. Thirty more arrests were made at the end after a small group threw "projectiles" at riot officers, the force said.
Belgium requires residents to show a Covid certificate to enter bars, restaurants, and cultural events, and there have been several recent street protests.
On Sunday, health minister Frank Vandenbroucke called, in a television interview, for a parliamentary debate on tighter rules as Belgium see Covid cases soar as the omicron variant takes hold.
"People's minds are changing," he said. "A year ago, I was saying: compulsory vaccination is not a good idea, we need to convince people.
"Now, knowing that we really need to vaccinate 100 percent of the population -- which was not our idea a year ago, we thought that 70 was enough -- we still need some sort of generalized takes up."
This is not an idea that is likely to find much support among the protesters, who carried the flags of a diverse array of political groups but were united in opposition to compulsory measures.
"It's a completely absurd crisis management which affects freedoms enormously and which will lead to a Chinese-style system if we let it happen," said one, who gave her name as Danielle.
Previous marches developed into running street battles with police, who have deployed tear gas and water cannon in recent weeks, but Sunday's ended in relatively orderly fashion amid tight security.
Riot police erected barbed wire barricades across roads leading towards the European Union's headquarters buildings and deployed drones and two water cannon trucks.
Between December 30 and January 5, Belgium recorded an average number of 17,513 new daily coronavirus infections, up 96 percent on the previous week and 169 hospitalizations per day, up 28 percent.