BERLIN -- People who are still not vaccinated as the fourth wave of the coronavirus pandemic takes hold in Germany must understand they have a duty to the rest of society to protect others, Chancellor Angela Merkel said on Thursday.

Merkel, speaking at the invitation of New Zealand Prime Minister Jacinda Ardern at an Asia-Pacific business summit, said it was the task of politicians to make the case for serious interventions by being honest with the public.

Coronavirus case numbers have surged across Europe in recent weeks, with experts worrying that health systems risk once again being overwhelmed, in part because unvaccinated people are still spreading the disease to the older and more vulnerable.

"We have to make it clear that I have the right to get vaccinated, and that is a great fortune, a huge achievement of science and technology," Merkel said over a video link. "But I also have a certain obligation to contribute to protecting society."

While many of the unvaccinated are in age groups that are statistically likely to experience less severe cases of COVID-19, they can pass the virus to older people with weaker immune systems, who can then end up in intensive care even with a vaccination.

Merkel, who was being interviewed by Microsoft president Brad Smith, added that the challenges of the pandemic and of climate change were similar, since they were both exponential processes whose severity was hard to recognise at the start of a growth curve.

"When you see the start of an exponential increase you have to act immediately, and an understanding of what exponential means isn't widespread in our societies," Merkel said.

"That's also why we have been so unconcerned about climate change - that also has exponential growth and we have to act at a time when it is not at all visible how the numbers will grow."