Trump got the treatment under a special access program offered by Regeneron. That drugmaker and Eli Lilly are the two furthest along in developing this type of drug.

The idea is to roll the treatments out more broadly under an FDA emergency authorization, and use them as a bridge to vaccination. Even if a vaccine is approved late this year, it will take months to get it to hundreds of millions of Americans and billions of people around the world.

But Warp Speed has so far spent less than $1 billion to support the development and manufacturing of three monoclonal antibody treatments, versus almost $10 billion on six vaccines. That choice may have slowed late-stage trials and manufacturing of the laboratory-made antibodies that fight Covid-19. And once monoclonal antibodies are approved, there may be shortages, said experts, including one of the drugmakers.

The manufacturing of antibody treatments, which are administered