SINGAPORE — Covid-19 is “permanent” and subsequent waves of infections will be a normal occurrence in the coming years, Singapore’s Foreign Minister Vivian Balakrishnan told CNBC.

“Covid-19 is endemic in humanity, which means it’s not ever going to go away completely,” Balakrishnan told CNBC’s “Squawk Box Asia” on Monday.

“And the reason it’s not going to go away completely is because it’s been widespread throughout the world, it’s sufficient critical mass, the rate of mutations and new variants will keep going, and the level of human immunity will also wax and wane,” he said.

The minister, who was a medical doctor before entering politics, also warned that now may be a “more dangerous period” for vaccinated people who may be complacent as well as those who are unvaccinated and lack protection against Covid.

Balakrishnan said vaccination is critical, and that people who have received Covid shots develop fewer symptoms and experience less severe disease, even when they’re infected. But vaccination alone is not the panacea to an “exponential explosion” in Covid cases.

That means measures such as social distancing and border restrictions may have to “come and go” in response to waves of Covid infections over the next two years, said the minister.

Singapore over the weekend tightened social restrictions after an increase in cases found in the community. Cumulatively, the country has confirmed more than 61,300 cases as of Sunday and 31 deaths, health ministry data showed.

Balakrishnan said around 20% of Singapore’s population has been vaccinated, but the government doesn’t have a defined threshold for when “herd immunity” would be reached. He explained that as new Covid variants emerge, the level of protection needed in a community so that the disease no longer transmits rapidly will change.

“As new variants keep evolving and as these new variants in fact appear to be more infectious than the original strain, the level of herd immunity mathematically will change,” said Balakrishnan.

“It is likely that the immunity from vaccination may also wane with time. So the point is, you can’t expect to say you’ve reached the magic figure and you’re suddenly immune and it’s mask off and no restrictions,” he added.

Singapore is a Southeast Asian city-state with no domestic air travel market. The country has reached an agreement with Hong Kong — a city that similarly has no domestic air market — to form a travel bubble that allows travelers to skip quarantine.

When CNBC asked whether the scheme is on track to begin on May 26, Balakrishnan said: “As of now the plan is yes, but we have to watch how the situation evolves over the next few days.”

The launch of the air travel bubble — initially slated for November 2020 — has been postponed multiple times after a spike in coronavirus cases in Hong Kong.

The two cities said last month that the scheme will start with one flight a day into each city, with up to 200 travelers on each flight.