The NIH said results of two studies of blood serum from people who had received Covaxin suggest that the vaccine generates antibodies that effectively neutralise the B.1.1.7 (Alpha) and B.1.617 (Delta) variants of SARS-CoV-2, first identified in the United Kingdom and India, respectively.
Fauci, 81, has been the National Institute of Allergy and Infectious Diseases director since 1984, and the chief medical adviser to the US President Joe Biden.
The trial began at the Kaiser Permanente Washington Health Research Institute in Seattle as the first participant received the investigational vaccine.
Last year Dr Fauci had largely dismissed the theory that the deadly COVID-19 virus, due to which over 165 million people have been infected worldwide and over 3.5 million peope died so far, was genetically engineered and had leaked from a lab in Wuhan, China.
The phase 3 trial is being implemented as part of Operation Warp Speed, a multi-agency collaboration led by the US Health and Human Services, which aims at accelerating the development and manufacturing of medical countermeasures for COVID-19 and delivering 300 million doses of an effective vaccine by January 2021.
The procurement and distribution will be centralised though the government is yet to take a call on the initial number of doses that will be procured.
The White House described the development as "quite good news".
Early data from its vaccine candidate 'mRNA-1273' showed it produced protective antibodies in a group of eight healthy volunteers, Moderna said. The other closely watched COVID-19 vaccine is the one being developed by scientists at Oxford University.
