Merck's full-year 2025 revenue guidance fell short of what some analysts were expecting, at a range of $64.1 billion to $65.6 billion.

The drugmaker’s guidance was affected by a pause in shipments of its top-selling vaccine to China from February through at least the middle of the year.

Shares of Merck are sliding in early trading after the drugmaker surprised Wall Street with a lower-than-expected 2025 sales forecast due partly to a pause in shipments of one of its top-selling products to China.