The United States final stage COVID-19 vaccine trial by Moderna Inc. and the National Institutes of Health began with the dosing of a single patient Monday morning in Savannah, Georgia.

The opening shot for testing that will weigh the vaccine's safety and efficacy in 30,000 people.

Moderna kicked off its phase 3 coronavirus vaccine study across 89 U.S. clinical research sites Monday, with results expected as early as November, government and health officials said. 

Patients will receive two doses of the mRNA-based shot about four weeks apart, with researchers comparing immune response between the vaccine and placebo arms two weeks after the second dose. 

Early results from the Moderna trial could be available in November or December, Anthony Fauci, the head of the National Institute of Allergy and Infectious Diseases, said on the call. But he called it "conceivable" that results could come as early as October if the trial enrolls very quickly in places with high case loads.

The trial is designed to show that the vaccine is at least 60% effective in preventing Covid-19, Fauci said.

Moderna's vaccine, co-developed with the NIH, is one of more than 160 in development to prevent the spread of the disease, and the World Health Organization estimates about 25 different inoculations are currently in human trials.