One in two Germans have received at least one dose of the coronavirus vaccine, health authorities said Friday, warning against complacency as the Delta variant is expected to become the dominant strain.

The variant first identified in India, now spreading fast in Britain and elsewhere, has doubled to just over 6 percent of all new infections in Germany during the week ending June 6 from the previous seven days.

"By the autumn, it will be the dominant strain," said Lothar Wieler, who heads the disease control agency RKI. 

It was "biologically logical" for the strain to become dominant simply because it was more infectious, he said.

Data from Britain, which has one of the fastest vaccination campaigns in the world, show that innoculation helps prevent serious disease.

Nevertheless, "that is valid only for fully vaccinated people," said Wieler, noting that those who have received only one jab could still catch the variant and spread it.

Around 29 percent of Germans are fully vaccinated.

Germany has eased most restrictions, reopening restaurants, shops, pools and museums in the last weeks as new infections dip sharply.

On Friday, it recorded 1,076 new cases, while the the number of new cases over a seven day period continued to drop to 10 per 100,000 people.

Wieler said however that it was necessary to keep wearing masks indoors, such as on public transport or at offices. 

"We have achieved really good results but the virus is still active and please let us give this virus no chance," he urged.