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.

Merck said on Tuesday it would not ship its HPV vaccine Gardasil in China until at least the middle of this year due to weak discretionary spending, a move that dented its full-year forecast and sent shares tumbling over 8% in premarket trading.

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.