Shutdown orders prevented about 60 million novel coronavirus infections in the United States and 285 million in China, according to a research study published Monday that examined how stay-at-home orders and other restrictions limited the spread of the contagion.

A separate study from epidemiologists at Imperial College London estimated that the shutdowns saved about 3.1 million lives in 11 European countries, including 500,000 in the United Kingdom, and dropped infection rates by an average of 82 percent, sufficient to drive the contagion well below epidemic levels.

The two reports, published Monday in the journal Nature, provide fresh evidence that aggressive and unprecedented shutdowns, which caused massive economic disruptions and job losses, were necessary to halt the exponential spread of the novel coronavirus.