A growing number of countries have reported confirmed cases of the new Omicron coronavirus variant, including Saudi Arabia and Nigeria

The number of unvaccinated people in Germany is still so large it risks overwhelming the country’s heath system, warned Health Minister Jens Spahn on Wednesday.

Even though the number of vaccinations is on the rise, 12 million adults out of a total of 69 million in the country are still not immunized against the coronavirus, Spahn wrote on Twitter.

Spahn, who only has a few days left in the job before the incoming government is sworn in, said that so far more than 10 million booster shots have been given out. Germany aimed to double that number by Christmas, he added.

Meanwhile, people queuing for booster shots in the capital Berlin on Wednesday endured long lines with wait times of up to three hours, CNN reported. In some instances, frustrated people left the lines before receiving their shot.

Germany is battling a fourth Covid-19 wave. It also has one of the lowest vaccination rates in western Europe, with a total 68.6% of eligible adults fully vaccinated, according to the country’s Health Ministry.