German biopharma company CureVac has announced that its COVID-19 vaccine candidate CVnCoV missed the prespecified statistical success criteria in a Phase II/III study.

According to results from the second interim analysis of the study, CvnCoV demonstrated an interim vaccine efficacy of 47% against COVID-19 disease of any COVID-19 disease.

In a statement, CureVac highlighted the ‘unprecedented context’ of the trial, adding that there were ‘at least 13 variants’ circulating within the study population subset assessed as part of the interim analysis.

Overall, 134 COVID-19 vases were assessed in the interim analysis, with 124 of these sequenced to identify the variant causing the infection.

According to the sequencing, only a single case could be attributed to the original SARS-CoV-2 virus, with over half of the cases having been caused by variants of concern (VoC),

Most of the remaining cases were caused by other less characterised variants such as Lambda or C.37, first identified in Peru (21%) and B.1.621, first identified in Colombia (7%).

“While we were hoping for a stronger interim outcome, we recognise that demonstrating high efficacy in this unprecedented broad diversity of variants is challenging,” said Franz-Werner Haas, chief executive officer of CureVac.

“As we are continuing toward the final analysis with a minimum of 80 additional cases, the overall vaccine efficacy may change. In addition, the variant-rich environment underlines the importance of developing next-generation vaccines as new virus variants continue to emerge,” he added.

CureVac said it had communicated the results with the European Medicines Agency – the study will continue to the final analysis, at which point the totality of data will be assess for the ‘most appropriate regulatory pathway’.