Correction to: Nature Biotechnology https://doi.org/10.1038/s41587-021-01121-0, published online 9 November 2021.

In the version of this News article initially published, a composition error in the first paragraph misstated the number of people who are affected by sickle cell disease globally. The figure has been amended to report that at least 4.4 million people are affected.

The online version of the article has been updated.