The vast majority of the 3.5 million employees covered by the mandate have been fully vaccinated, Xinhua news agency quoted the senior administration official as saying to the National Public Radio (NPR) on Monday.
An additional 5 percent of workers have requested or received an exception or an extension, the official said.
Biden announced in September that the 3.5 million-strong federal workers were required to undergo vaccination, with no with option to get regularly tested instead, unless they secured an approved medical or religious exemption.
Their vaccination pace was far ahead of the national rate, which is yet to reach 70 percent.
On November 19, White House Press Secretary Jen Psaki had said that experience with other similar mandates in the private sector indicated there could be a last minute rush to meet the requirements and submit paperwork.
The small percentage of federal employees who don't comply with the mandate as of Monday won't face immediate dismissal.
Agencies will continue processing documentation and considering exemptions, including for documented medical necessity.
There will be education and counseling for employees who haven't complied.
Till date, a total of 230,298,744 people have received at least one dose of Covid-19 vaccine, making up for 69.4 per cent of the entire US population.
Fully vaccinated people stood at 196,284,442, accounting for 59.1 per cent of the total.
A total of 35,393,770 people, or 18 per cent of the fully vaccinated group, have received booster shots, according to federal data.