Will Weak Gardasil Sales Continue to Be a Drag on MRK's Top Line?

Merck (MRK) reported a significant 48% year-over-year decline in Gardasil sales to $2.45 billion in H1 2025, primarily due to weak demand and high channel inventory in China and Japan, leading the company to halt shipments to China until at least year-end and withdraw its 2030 sales guidance for the vaccine. This top-line pressure was exacerbated by sales declines across other established vaccine products, while its newly approved RSV antibody, Enflonsia, faces intense market competition. Consequently, MRK shares have underperformed year-to-date, reflecting investor concerns over persistent revenue headwinds despite the stock's relatively attractive valuation.

Analysis

Merck is facing significant top-line pressure centered on its second-largest product, Gardasil, which saw sales plummet 48% year-over-year to $2.45 billion in the first half of 2025. This downturn is primarily driven by weak demand and high channel inventory in China, prompting the company to halt shipments to the region until at least the end of 2025 and, more critically, withdraw its long-term guidance for Gardasil to exceed $11 billion in sales by 2030. The issue appears systemic within the vaccine portfolio, as other products like ProQuad, Rotateq, and Pneumovax 23 also experienced sales declines. While the June 2025 US approval of its RSV antibody, Enflonsia, offers a potential new revenue stream, it enters a highly competitive market against AstraZeneca/Sanofi's Beyfortus, which is already experiencing robust 79% sales growth. The market has priced in these concerns, with MRK's stock down 15.4% year-to-date, significantly underperforming the industry. The stock's current forward P/E of 8.98x, while appearing attractive relative to the industry and its historical average, reflects the market's deep concerns over deteriorating fundamentals and diminished growth visibility.

Key Decisions for Investors

• Investors should weigh the stock's low forward P/E of 8.98x against the severe fundamental headwinds, recognizing the risk of a value trap given the withdrawal of long-term Gardasil guidance and broad weakness in the vaccine portfolio.
• Closely monitor future earnings for signs of Gardasil sales stabilizing in markets outside of China and Japan, as well as initial sales figures for Enflonsia to gauge its penetration against entrenched and rapidly growing competitors.
• Given the halt in Gardasil shipments to China is now extended through at least a full year, positions should be evaluated based on a revised, lower growth outlook for Merck's vaccine franchise in the medium term.