Scientists have backed Brazil's drug regulator's decision to stop the import of Russia's Sputnik V coronavirus vaccine on the basis that batches they tested carried a live version of a common cold-causing virus.

Top virologist Angela Rasmussen told AFP the finding “raises questions about the integrity of the manufacturing processes” and could be a safety issue for people with weaker immune systems, if the problem were found to be widespread.

Russia's Gamaleya Institute, which developed the vaccine, has denied the reports.

The issue centres around an “adenovirus vector” — a virus that normally causes mild respiratory illness but in vaccines is genetically modified so that it cannot replicate, and edited to carry the DNA instructions for human cells to develop the spike protein of the coronavirus.