Mr. Biden has either donated or pledged about 600 million vaccine doses to other countries — a small fraction of the 11 billion that experts say are needed to slow the spread of the virus worldwide. His administration has also taken steps to expand Covid-19 vaccine manufacturing in the United States and India, and is supporting production in South Africa and Senegal to expand access to locally produced vaccines in Africa.

But with the administration now recommending booster doses for vaccinated Americans starting next month, outraged public health experts and many Democrats on Capitol Hill are calling on the president to move more aggressively to scale up global manufacturing. In an analysis to be published on Thursday, the AIDS advocacy group PrEP4All found that the administration had spent less than 1 percent of the money that Congress appropriated for ramping up Covid-19 countermeasures on expanding vaccine manufacturing.

Congress put a total of $16.05 billion in the American Rescue Plan this year, in two separate tranches, that could be used to procure and manufacture treatments, vaccines and tools for ending the pandemic. But PrEP4All found that all told, the administration had spent $145 million — just $12 million of it from the American Rescue Plan — to expand vaccine manufacturing.