Moderna Jumped 177% in a Day. The Math Behind It Doesn’t Quite Add Up.

Moderna shares rose 177% in a single session this week — the largest one-day move by an S&P 500 company in over two decades — after positive late-stage data on a personalized melanoma vaccine it’s developing with Merck. From a medical standpoint, it’s as promising a result as this technology has produced. From a market-math standpoint, the numbers don’t entirely reconcile.

Analysts at Leerink Partners model low-single-digit billions in annual sales for the vaccine by 2032. Even their bull case of $10 billion in peak sales supports roughly $40 billion of added value across the Moderna-Merck partnership. Yet in the days following the data, Moderna, Merck, and BioNTech collectively added about $80 billion in combined market value — and Moderna alone went from roughly $25 billion to near $60 billion, more than the bull-case math would seem to support on its own.

Part of the disconnect may be that melanoma was actually the easiest target on this platform’s roadmap. The vaccine can be built against up to 34 mutations, but typically only two or three produce a meaningful immune response — and melanoma tends to have mutations to spare while also responding unusually well to immunotherapy already. The cancers next in line look tougher: kidney cancer offers fewer usable targets, bladder cancer presents a more suppressive tumor environment, and pancreatic cancer offers “next to none of the above,” in the words of one analyst note.

Pricing adds another layer of uncertainty. Comparable personalized therapies run around $300,000 per course, with gross margins landing between 50% and 80% — well below the 90%-plus margins typical of conventional blockbuster drugs.

The real test comes when fuller data is presented at an upcoming medical conference, along with the price tag that follows. That’s when investors will find out whether the market’s enthusiasm was well ahead of the science, or right on time.