German biopharmaceutical company CureVac's mRNA-based vaccine has shown efficacy of just 47 per cent against Coronavirus disease, the lowest reported so far from any Covid-19 vaccine maker.

The trial of vaccine candidate CVnCoV, which included nearly 40,000 volunteers from 10 countries, did not meet pre-specified statistical success criteria, according to the preliminary results of a clinical trial reported on Wednesday.

"The variant-rich environment underlines the importance of developing next-generation vaccines as new virus variants continue to emerge," said Franz-Werner Haas, Chief Executive Officer of CureVac, in a statement.

The vaccine maker assessed 134 Covid-19 cases in this interim analysis. Out of these cases, 124 were sequenced to identify the variant causing the infection. The trial will continue with a minimum of 80 additional cases and the final analysis is expected in two to three weeks, the company said.

"We're going full speed for the final readout. We are still planning to filing for approvala Haas was quoted as saying by the New York Times.

The results caught scientists by surprise. The vaccine is made from engineered mRNA, the same technology used by the Pfizer-BioNTech and Moderna vaccines. And CureVac's shots yielded promising results in animal experiments and early clinical trials.

According to Haas, the disappointing results were due to the high number of virus variants in the countries where the vaccine was tested -- latin America and Europe. Out of 124 of the Covid-19 cases that the company's scientists genetically sequenced, only one was caused by the original version of the coronavirus.

More than half of the cases (57 per cent) were caused by Variants of Concern. Most of the remaining cases were caused by other less characterised variants such as Lambda or C37, first identified in Peru (21 per cent) and B1621, first identified in Colombia (7 per cent).

In this context, the interim results suggest efficacy in younger participants but did not allow to conclude on efficacy in the age group above 60, the company said.

The results should serve as a wake-up call for the threat that new variants can pose to the effectiveness of vaccines, Haas was quoted as saying by the NYT. CureVac is searching for new RNA molecules that can work against many variants at once, as well as combining RNA molecules tailored to different variants in a single dose. "It's a new Covid reality, that's for sure," he said.