The upgrade is driven by the improved leverage due to the group’s strong growth and resilience to macroeconomic headwinds.

The Positive Outlook is driven by the expectation that the greatly improved credit metrics will be sustained.

The ratings reflect the company's strong deleveraging focus after the Versum acquisition, its limited exposure to the coronavirus crisis and the expectation that it will deliver on its pharma pipeline.

The rating reflects Merck's strong divisional portfolio, including credit-supportive underlying industries, and the expectation that credit metrics will improve after the acquisition of Versum.

The ratings continue to reflect our view of Merck's credit supportive business risk profile around its three critically sized divisions. It also reflects our view on management's conservative financial policy driving for continuous deleveraging.