A Chinese scientist who caused outrage last year when he said he had created the world’s first “gene-edited” babies in an attempt to protect them from HIV may also have put them at risk with a “foolish” choice of gene, experts say.

He Jiankui, then an associate professor at the Southern University of Science and Technology in Shenzhen, China, sparked an international scientific and ethical row when he said he had used CRISPR-Cas9 technology to alter the embryonic genes of twin girls born in November 2018.

He said he had targeted a gene known as CCR5 and edited it in a way he believed would protect the girls from infection with HIV.

But in a study published in the journal Nature Medicine on Monday, scientists found that people with two copies of a so-called ‘Delta 32’ mutation of CCR5, which can protect against HIV infection, also had a significantly higher risk of premature death.