Two Chinese babies whose genes were allegedly edited to make them resistant to HIV are more likely to die young and would have been better off without the treatment, a study has found.

Last year Chinese biophysicist He Jiankui outraged the scientific community when he announced the birth of the world’s first genetically edited humans.

He claimed to have deliberately altered mutations to the CCR5 gene, in an attempt to mimic the roughly 10 per cent of people of European origin who are naturally resistant to HIV.

It is the first time a scientist has altered a human germline, the heritable genetic code.

He was roundly criticised for breaching ethical rules, sacked from his university and censured by the health ministry of Guangdong.

Now a study by Berkley University in California has shown that people with that combination of mutations are 21 per cent more likely to die at a young age than the general population.

They believe that while the so-called Delta 32 mutation of the CCR5 gene does protect against HIV, it weakens the body’s defences against influenza and possibly other viruses.

Published in the journal Nature Medicine, the study looked at 400,000 genomes - full genetic codes - and associated health records contained on a British database, the UK Biobank.