A broad rally in vaccine stocks helped BioNTech clinch its best day in six years. That momentum may not last.

On Wednesday, shares of the German biotech surged 22% to $113.12 for their largest same-day gain since April 2023. The rally followed late-stage trial data indicating that a combination of Moderna's personalized cancer vaccine and Merck's Keytruda was more effective at preventing melanoma recurrence than Keytruda on its own.

BioNTech was just one of the vaccine makers that got a boost. Shares of Novavax, which is pursuing research collaborations in oncology vaccines, jumped 11% as Moderna's stock nearly tripled.

The results are a positive for cancer vaccine-linked stocks more broadly, Leerink Partners analysts noted. However, they no longer see BioNTech as a clear winner in the category, and expect the latest gains to fade.

It might seem like a difficult argument to swallow, considering BioNTech was one of earliest pioneers of mRNA cancer vaccines. The drugmaker's neoantigen mRNA cancer vaccine program is centered around its proprietary iNeST platform-an acronym for Individualized Neoantigen Specific Immunotherapy.

Developed jointly with Roche subsidiary Genentech, these customized treatments analyze specific mutations to stimulate a precise, multi-target immune response against solid tumors.

BioNTech is advancing several mRNA cancer therapies simultaneously, split between personalized vaccines and off-the-shelf options. But BioNTech's pipeline has moved more slowly than Moderna's, whose cancer vaccine intismeran autogene triggered Wednesday's stock surge.

There have been notable setbacks. In late 2025, BioNTech paused development of its BNT111 cancer vaccine candidate in advanced refractory melanoma. The company had been testing the candidate in combination with Regeneron's checkpoint inhibitor, Libtayo, during a Phase 2 study.

Leerink believes BioNTech's prospects of becoming a leader in the space have dimmed significantly, to the point where that potential is no longer priced into the stock.

Analysts appear to be shifting their focus to other assets in the company's oncology portfolio. Goldman Sachs analyst Asad Haider highlighted BioNTech's pumitamig in a recent note, calling its non-small cell lung cancer data "encouraging" even with a competitor's drug further along in development.

Near-term concerns and uncertainty may also take precedence. BioNTech is navigating an upcoming leadership transition, as its husband-and-wife co-founders are set to exit by year's end to launch a new start-up. BioNTech has pledged to license its mRNA technology in exchange for a minority stake, milestone payments, and sales royalties.

Second-quarter earnings offered little reassurance, signaling that the company is struggling more than Covid-vaccine partner Pfizer to define its post-pandemic future. Plummeting Covid revenue continues to dominate top-line performance, forcing the company to issue full-year revenue guidance that fell short of analyst expectations.