Speaking on Tuesday, Wieler urged people to spend Christmas in very small groups and limit contacts to the same few participants.
“We are in for some tough weeks. We shouldn't make them even harder for ourselves,” the RKI boss said. “If people from different regions meet all over Germany, then the virus can spread even faster.”
He said that the tougher new lockdown measures had so far had no impact on the spread of the virus, with cases continuing to rise.
Figures released on Tuesday morning show a further 19,528 positive tests, with 731 more deaths.
The nationwide number of new infections per 100,000 inhabitants within seven days rose to an all-time high of 198 on average on Tuesday. The federal government and the Bundesländer want to bring that figure down to below 50.
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Currently, though, six states have an incidence level above the 200 mark. The infection rate on Saxony, the worst in the country, is double that figure.
The tighter lockdown measures will last until at least January 10th. At that point the states are legally obligated to either lift the restrictions or renew them.
Vaccines to come
Wieler said he was happy that the first vaccinations would arrive shortly after Christmas but cautioned that it would take a long time before the majority of people are vaccinated and the virus' spread could be controlled through 'herd immunity'.
“That makes it all the more important to reduce the infection figures and keep them permanently low so that we can regain a certain degree of normality as soon as possible in the new year,” he said.
Following Monday's EU approval of Mainz-based Biontech's vaccine, Germany is scheduled to receive a first shipment of some 150,000 doses of the jab on Saturday.
In total, more than 1.3 million doses are expected to be distributed across the country by the end of the year. That will be followed by weekly deliveries of 670,000 doses, Health Minister Jens Spahn has pledged.