German Chancellor Angela Merkel urged unvaccinated people to reconsider their decision in a video message on Saturday, as the German army prepares to step in.
The country's seven-day coronavirus incidence rate rose to the highest level since the pandemic began.
"Difficult weeks lie ahead of us, and you can see that I am very worried," Merkel said, speaking in her weekly video podcast. "I urgently ask everyone who has not yet been vaccinated: please reconsider."
The German army is preparing to mobilise 12,000 soldiers by Christmas to assist overrun healthcare services, Spiegel newspaper reported, and will provide booster vaccinations and tests in care homes and hospitals.
So far, 630 soldiers have been deployed, Spiegel reported. The army was not immediately available for comment.
Germany's seven-day incidence rate - the number of people per 100,000 to be infected over the last week - rose to 277.4 on Saturday, data from the Robert Koch Institute showed. The record in the third wave of the pandemic last December was 197.6.
The federal government and leaders of Germany's 16 states are due to meet next week to discuss tightening measures, though the three parties negotiating to form a new government have agreed to let a state of emergency in place since the start of the pandemic expire on Nov. 25 as planned.
"It has always helped us when states and the federal government worked together and committed to uniform rules," Merkel said.
Europe has become the epicentre of the pandemic again, prompting some governments to consider re-imposing unpopular lockdowns in the run-up to Christmas and stirring debate over whether vaccines alone are enough to tame COVID-19.