"It will only be a small delivery at first," Spahn told an online event, adding he expected a shipment of around 275,000 doses in the week of April 12.
J&J's shot, which was approved by European Union regulators on March 11, is the fourth to be endorsed for use in the EU after vaccines from Pfizer-BioNTech,, AstraZeneca-Oxford University and Moderna.
Critics blame German bureaucracy and slow decision-making as well as an over-reliance on European Union approval and supply deals.
"But the vaccination numbers will not immediately grow to 20 million a month or to 10 million a week," he told ZDF television. "In April there will be significantly more vaccinations, but not on that scale."
"There needs to be an overall shutdown in society for all of us, also around the turn of the year," Spahn told the Bundestag lower house of parliament.