Anyone who has been infected with the corona virus is only considered to have recovered for three months.
The reason for this is the new omicron variant of the pathogen.
From a scientific point of view, the Robert Koch Institute (RKI) has halved the six-month period, said a spokesman for the Federal Ministry of Health on Monday in Berlin.
Because of the predominant omicron variant, there is a greater risk of falling ill again after this time or of transmitting the virus to others.
The new requirement is linked to an ordinance passed by the Federal Council on Friday and has been in effect since Saturday.
"These specifications are checked regularly and can change according to the state of the art," said the RKI.
It is up to the federal states to determine how the shortening of the period will affect the applicable 2G and 3G corona rules.
The RKI gave the seven-day incidence on Monday morning as 528 cases per 100,000 inhabitants.
Federal Health Minister Karl Lauterbach (SPD) does not want to work out his own proposal for general vaccination.
"As Federal Minister of Health, you have to respect when a decision is a conscientious decision of Parliament," said Lauterbach on Monday in Schwerin during his first visit to Mecklenburg-Western Pomerania.
Lauterbach also commented on the statements of the virologist Christian Drosten, who sees an opportunity in the milder omicron variant and said that sooner or later everyone will have to be infected with the virus.
Lauterbach did not evaluate Drosten's statement as taking sides for or against compulsory vaccination.
The scientist from the Berlin Charité had also pointed out the importance of vaccination, especially for older people.
It is precisely this age group that he does not want to endanger by loosening too early, said Lauterbach.
Personally, he is in favor of compulsory vaccination, which also includes the so-called booster vaccination.