US officials preparing to roll out Covid-19 booster shots in the face of waning vaccine protection and surging hospitalisations and deaths caused by the highly contagious Delta variant are hoping boosters might prevent mild cases as well, according to Reuters.

In theory, that could reduce virus transmission — a goal officials have been less explicit about — and hasten America's recovery.

"It is not the primary reason (for boosters), but it could actually be a very positive offshoot,” Dr. Anthony Fauci, one of the Biden Administration's Covid-19 advisers and the nation's top infectious disease doctor told Reuters.

The main reason for boosters, Fauci said in a telephone interview, is to reverse the trend of rising “breakthrough” infections among people who are fully vaccinated, a point that many experts dispute.