WASHINGTON, United States (AFP) — The US will begin in mid-March a clinical trial of a version of Moderna's COVID vaccine specific to the South Africa variant, Anthony Fauci, the top advisor to the White House on the pandemic, said Friday.

The Phase 1 trial will involve 210 people to study both the immune response generated by the vaccine and its safety, he said.

Unlike previous trials there will be no placebo, and instead the experiment will look at various combinations of the new vaccine and the old, both in people who were previously vaccinated and in people who have never before been vaccinated.

The goal is to determine how well the different strategies compare in their ability to neutralize the B.1.351 strain, which has been shown to partly reduce the effectiveness of the current generation of vaccines.

Carrying out the early-stage trial "does not necessarily mean a commitment to make 300 million, or 600, million doses of this vaccine," said Fauci.

"This is all going to depend on the dynamics of the outbreak and what other variants might be dominant."

The Food and Drug Administration said earlier this week that variant-specific COVID vaccines would likely not need to go through the same level of clinical testing that the first versions did before they receive authorisation.