Merck reported strong fourth-quarter earnings driven by key products like Keytruda and newer drugs such as Winrevair, with revenue of $16.4 billion and net income of $2.96 billion. Keytruda sales increased by 7% to $8.37 billion, supported by higher demand for early and metastatic cancer treatments. However, sales of Gardasil, the HPV vaccine, declined by 34% to $1.03 billion due to halted shipments to China and reduced demand following CDC vaccine schedule changes. Merck's animal health division grew by 8% to $1.51 billion. Despite quarterly successes, Merck issued a modest 2026 revenue guidance of $65.5 to $67 billion, below analyst expectations of $67.6 billion, and an adjusted earnings forecast of $5 to $5.15 per share, also below estimates. The outlook reflects anticipated revenue losses from patent expirations of key drugs like Januvia, Janumet, and Bridion, and a one-time $9 billion charge related to the acquisition of Cidara. The company is also facing challenges from generic competition and soft demand for Gardasil, especially in China, where shipments have been halted. Merck aims to offset upcoming patent expirations and revenue declines through cost-cutting measures, including a $3 billion reduction by 2027, and efforts to boost sales of newer formulations like the subcutaneous Keytruda. The company's stock declined 2.5% in premarket trading following the outlook announcement.