CureVac's COVID-19 shot just failed in a large trial, a major setback for the Gates-backed biotech

• CureVac's experimental COVID-19 vaccine failed in a pivotal clinical study, the biotech said Wednesday.
• It's the first late-stage study to flop, with CureVac's vaccine showing 47% effectiveness.
• The German biotech saw its stock price drop by more than 50% in post-market trading.
• See more stories on Insider's business page.

A COVID-19 vaccine candidate developed by the German biotech CureVac failed in a critical late-stage study, the company said Wednesday.

It's the first failure of a major vaccine candidate in a final-stage trial. CureVac said an interim analysis showed the shot was 47% effective, falling short of the company's target and health officials' standards for coronavirus vaccines. European officials had already secured more than 225 million doses of the shot.

The trial is still ongoing and the final vaccine efficacy figure may vary as more COVID-19 cases are tallied. The interim analysis is based on 134 illnesses. In a statement, CureVac leaders said that virus variants played a role in the result.

"While we were hoping for a stronger interim outcome, we recognize that demonstrating high efficacy in this unprecedented broad diversity of variants is challenging," CureVac CEO Franz-Werner Haas said in a statement.

The company, which is backed by The Bill & Melinda Gates Foundation, saw its stock price plummet following Wednesday's announcement. Shares were down more than 50% in post-market trading.