The head of Germany's Robert Koch Institute (RKI) for disease control on Wednesday said he expected the country's recent decline in new coronavirus infections to be reversed.

Lothar Wieler warned that the transmissibility of the omicron variant meant that it would be the dominant form of the virus by mid-January.

That development, he stressed, meant there was an infection wave of "unseen momentum" threatening to overwhelm the health care system.

"In the past few days, the number of cases has been declining, but unfortunately, this is not a sign of easing," he told a press conference in Berlin. "We need to get the still very high case numbers down.

"Christmas must not be the spark that lights the omicron fire."

Meeting on Tuesday, Germany's federal and state leaders agreed to impose contact restrictions — including for vaccinated and recovered individuals — starting next week.

However, German Health Minister Karl Lauterbach agreed that a fifth wave could no longer be prevented. 

"We are in a situation where we are managing to slowly get the wave under control with the delta variant," he told the same press conference. "Nevertheless, we have to expect a fifth wave now for sure."

The minister said booster vaccines were central to the fight against the virus, with effectiveness in preventing severe cases at more than 90%. "It appears that the protection against severe disease is very high," said Lauterbach, a trained epidemiologist who took over the ministerial role earlier this month.

Lauterbach also revealed that Germany has ordered 80 million doses of an omicron-specific vaccine on order from BioNTech. However, delivery is not expected to take place until April or May.

The main vaccine being used in the current booster campaign is Moderna, Lauterbach said, adding that Germany had also ordered 4 million doses of the new Novavax jab.

What are the latest measures?

New regulations due to come into effect "at the latest" on December 28 are aimed at dissuading people from holding and attending large New Year's Eve celebrations amid concerns over the omicron variant.

Under the new measures, a maximum of 10 people who have been vaccinated or recovered from COVID-19 would be allowed to attend a private gathering.

In cases when an unvaccinated person is present, only one other household would be able to attend. The new capacity limits will apply to both indoor and outdoor celebrations.

Access to restaurants remains limited to people who could provide proof of vaccination or recovery.

For large events, spectators will be banned from sporting events, cultural shows, concerts and other large public events.

Green Party lawmaker defends coalition decision to delay new restrictions

Opposition Bundestag members have questioned the delay on the measures, suggesting they should come into effect before Christmas, but in an interview with DW on Wednesday Green Party lawmaker and radiologist Paula Piechotta defended the government's decision.

"What we've agreed on now is one of the most potent non-pharmaceutical measures against COVID, meaning contact restrictions to 10 people," she said, adding the holidays themselves "are kind of a natural COVID breaker because schools are closed, universities are closed, a lot of businesses are closed. So we are thinking that for now, this is quite an adequate response."

Of the omicron variant, Piechotta said: "No one can say that we are not alarmed and that we are not communicating, that the situation with omicron is quite severe."

Meanwhile, the government hopes "to achieve 80% vaccination rate by January," she noted.

Mandatory vaccines on horizon?

Germany's Ethics Council on Wednesday said it was in favor of mandatory vaccinations for all adults over the age of 18. National and state leaders asked the body for its assessment earlier this month, with Germany battling a fourth wave of the COVID-19 pandemic.

Germany registered 45,659 new confirmed cases of coronavirus infection on Wednesday, according to the Robert Koch Institute. That figure brings the total number of confirmed cases in the country since the start of the pandemic up to 6,878,709.

The institute reported 510 new deaths from the coronavirus, with 109,324 deaths since the start of the pandemic.

The RKI has recommended that Germany immediately implement "maximum contact restrictions" and "maximum infection prevention measures."

jsi, rc/rt (AFP, dpa, Reuters, dpa)