A volunteer receives a dose of CureVac vaccine or a placebo during a study by the German biotech firm CureVac as part of a testing for a new vaccine against the coronavirus disease (COVID-19), in Brussels, Belgium March 2, 2021.Yves Herman | ReutersCureVac stock plunged 50% in extended trading Wednesday after the German biopharmaceutical company released preliminary efficacy results for its Covid-19 vaccine candidate that failed to meet success criteria.The vaccine candidate demonstrated an interim efficacy of 47% against Covid-19 disease “of any severity,” according to a press release. The company said final analysis of the results would be completed in the coming weeks. The late-stage clinical trial of approximately 40,000 participants across 10 countries found high prevalence of virus variants, in particular the lambda strain first detected in South America. “While we were hoping for a stronger interim outcome, we recognize that demonstrating high efficacy in this unprecedented broad diversity of variants is challenging,” CEO Franz-Werner Haas said in a statement. “As we are continuing toward the final analysis with a minimum of 80 additional cases, the overall vaccine efficacy may change.” The study also found varying levels of efficacy for different age groups, according to the release. CureVac is also working on a separate Covid vaccine candidate in partnership with GlaxoSmithKline. The companies expect to enter clinical testing on that candidate in the third quarter of 2021, CureVac said Wednesday.