Merck Gardasil Legal Risk Compounds Vaccine Woes as Trial Looms

What happened

Merck's Gardasil franchise faces a new headwind: a personal injury trial in Los Angeles over alleged side effects, adding litigation risk to an already strained vaccine business that saw sales plunge from $8.6B in 2024 to $5.2B in 2025 due to China's shipment halt. Although Merck has not disclosed material Gardasil litigation reserves in its filings, this first bellwether case could set a precedent for thousands of similar claims, potentially creating a multi-year liability overhang. The trial comes at a time when Merck is already navigating a ~$2.5B FY2026 headwind from generic/IRA pressures and a paused China restart, with Gardasil expected to see no material improvement in China sales through 2026. While the DeepValue report's base case already assumes Gardasil weakness, the addition of litigation risk further impairs the vaccine's recovery narrative and could pressure cash flows if settlements or judgments become material. The stock's current price of ~$119 reflects the broader Keytruda-exclusivity transition but may not fully discount the compounding effect of legal costs on an already challenged product line.

Implication

Investors should monitor the Gardasil trial closely for signaling on settlement ranges or jury verdicts. If Merck prevails or settles for a manageable sum, the overhang lifts, potentially allowing the stock to reprice toward the base case of $125. However, a large adverse verdict would validate the bear scenario ($95) by adding a new multi-year liability on top of China disruption and Keytruda LOE. The thesis delta is that Gardasil now faces operational, regulatory, and legal headwinds simultaneously, increasing the probability of the bear case from 25% to 35-40% until the legal path clarifies.

Thesis delta

The Gardasil trial introduces a previously unmodeled litigation risk that compounds the existing China inventory and local-competitor threats. While the DeepValue report's bear case considered China risk, it did not explicitly incorporate a potential legal liability that could require billions in settlements or judgments. This raises the probability of the bear scenario and pushes the re-assessment window further out, as investors will demand clarity on both China shipments and legal exposure before re-rating the stock.