LONDON – A paper that raised concerns for the future health of Lulu and Nana, the world's first gene-edited babies, has been fully retracted at the request of the authors, after they failed to identify a problem in data from the U.K. Biobank on which their analysis was based. The study published in Nature Medicine in June, concluded the edits the twin girls are purported to have in their CCR5 chemokine receptor gene is associated with a 21% increase in mortality in middle and old age.