Daily newsletter · Fri 23 Oct 2026
Moderna fell 17.57% after its cancer vaccine results leaked two days early
Moderna closed Thursday at US$202.63, down 17.57%. At its worst the stock was down 25%, and trading was briefly halted.
The leaked results were good. Moderna and Merck are testing a personalised cancer vaccine alongside Keytruda, Merck's immunotherapy drug, in melanoma patients who have had surgery. The leaked figures showed the pairing cut the risk of the cancer returning, or of death, by 42% compared with Keytruda alone.
The numbers appeared on the medical news site Oncology Central at about 12.30pm in New York and were quickly taken down. They were due to be presented at the European Society for Medical Oncology congress on Saturday.
Investors sold anyway. Moderna had risen more than 500% this year before Thursday, so a great deal of good news was already in the price.
Merck, whose business depends far less on this one vaccine, fell less than 2%.
The full presentation comes on Saturday in Europe. The leaked figures measure whether the cancer came back. Whether patients live longer is a separate measure, and it is the one I'd want to see before deciding what this vaccine is worth to Moderna.
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