Earlier in the day, Seibert said Merkel had been “doing well” in self-imposed quarantine.
The chancellor had decided to self-isolate as a precaution after learning on Sunday that a doctor who vaccinated her last Friday was infected with the novel coronavirus.
“The chancellor is doing well,” Seibert told reporters.
It came as the head of Germany’s disease control agency the Robert Koch Institute on Monday said he was “optimistic” that the restrictions were paying off, noting that the outbreak’s “exponential growth curve had started to flatten a bit”.
Lothar Wieler said he expected to have a clearer view of the trend by Wednesday.
Dialling in from her Berlin flat, Merkel, 65, led a cabinet meeting that decided on a major rescue package for virus-stricken companies and employees in Europe’s top economy.
Earlier in the day Seibert thanked everyone on Merkel’s behalf for “the many, many well wishes and messages for the chancellor to stay healthy”.