Prices of precious metals tumbled on Monday after trial results of AstraZeneca's COVID-19 vaccine candidate showed that the shot is 70% effective in preventing the disease, prompting optimism among investors.

Over the weekend, the government's adviser Dr. Moncef Slaoui revealed mass vaccination in the United States might start early-December following the green light from the Food and Drug Administration, while the agency approved Regeneron Pharmaceuticals' drug used in treating the coronavirus symptoms.

Spot gold fell 1.62% to sell for 1,842.82 per ounce at 10:07 am ET, while silver sank 2.37% to $23.65 per ounce and platinum 1.83% to $935.02. On the other hand, palladium rose by 0.56% to go for $2,341.64 an ounce.