The shortage of vaccines to combat a fast-growing monkeypox outbreak was caused in part because the Department of Health and Human Services failed early on to ask that bulk stocks of the vaccine it already owned be bottled for distribution, according to multiple administration officials familiar with the matter.

By the time the federal government placed its orders, the vaccine’s Denmark-based manufacturer, Bavarian Nordic, had booked other clients and was unable to do the work for months, officials said — even though the federal government had invested well over $1 billion in the vaccine’s development.

The government is now distributing about 1.1 million doses, less than a third of the 3.5 million that health officials now estimate are needed to fight the outbreak. It does not expect the next delivery, of half a million doses, until October. Most of the other 5.5 million doses the United States has ordered are not scheduled to be delivered until next year, according to the federal health agency.