Moderna Inc. stock skyrocketed in the extended session Tuesday after the biotech company said its experimental coronavirus vaccine produced a “robust” immune-system response in a larger group of people and the study will move to a larger clinical trial in July.

Results published in The New England Journal of Medicine showed that a two-dose vaccination schedule induced the desired immune response in all 45 people evaluated, a larger group than in the preliminary data Moderna MRNA, +4.54% released in May, and was generally safe and well-tolerated.