Shares of Moderna Inc. /zigman2/quotes/205619834/composite MRNA +0.46% jumped 25.1% in premarket trading on Monday after the biotechnology company announced positive results from a Phase 1 clinical trial for its experimental mRNA coronavirus vaccine. The trial was done in partnership with the National Institute of Allergy and Infectious Diseases. Within 43 days and after two doses, the participants taking one of two dosing levels of the vaccine candidate reported the same or higher level of antibodies as in blood samples gathered by patients who have recovered from COVID-19, the company said. There were four adverse events during the trial, including one participant who reported a severe skin reaction where the investigational vaccine was administered. "These interim Phase 1 data, while early, demonstrate that vaccination with mRNA-1273 elicits an immune response of the magnitude caused by natural infection starting with a dose as low as 25" micrograms, Moderna chief medical officer Dr. Tal Zaks said in a news release. The next step is a Phase 2 trial, which has been approved to move forward by the Food and Drug Administration. It will focus on two dosing levels (50 microgram and 100 microgram). The early-stage trial had a third dosing level, 250 micrograms. Moderna's vaccine candidate is widely viewed as a frontrunner in the effort to develop the first vaccine for the virus. The preclinical company said earlier this month that the Phase 2 trial will begin "shortly," and on Monday it said it expects a Phase 3 trial to begin in July, if the vaccine is successful in the mid-stage trial. Moderna's stock has soared 240.9% year-to-date. The S&P 500 /zigman2/quotes/210599714/realtime SPX +0.06% , in comparison, is down 11.3%.