As word spread in 2018 about the birth of the world's first genetically altered children, concerns about their future health were mounted, with a study even raising the tragic possibility of shortening lives for newborns. That risk now seems much less likely.
The disturbing document published in Nature in June last year has now been withdrawn by the authors themselves, who in the wake of criticism acknowledge how they searched for signs of a mutated gene in a data sample that left too much room for doubt.
It is an important lesson not only in how science values self-correction, but how researchers need to tread lightly when trawling through population-size databases in search of new discoveries.
"I feel I have a responsibility to set the record straight for the public," University of California population geneticist Rasmus Nielsen told Ewen Callaway at Nature .
The gene at the center of research serves as a template for a receptor on white blood cells.
Called CCR5, its usual task is to detect chemical signals used in immune responses. Unfortunately, the deadly human immunodeficiency virus (HIV) was developed to use it as a window to gain entry into the cells.
Ever since the receptor's role in HIV infection was discovered, researchers have wondered how important this receptor really is. Would we really miss it if it was gone?
Fortunately, an answer can be found among a percentage of people of European descent with a naturally occurring "broken" version of CCR5 called delta-32. Those carrying a single copy of the delta-32 variant appear to be less susceptible to HIV than the rest of the population.
In November 201
Han Jiankui's first announcement suggested that at least one of the twins had two altered CCR5 genes. Although they do not seem to match the delta-32 variants, it was enough to invite speculation about what kind of life the children can have.
HIV resistance is undoubtedly a good thing in a world where the disease it causes is still destroying for many lives. But these benefits for any individual may not be so great if a low-quality CCR5 receptor increases the risk of developing other health problems.
Nielsen and his colleagues intended to answer this question by looking for similar altered versions of the CCR5 gene in the UK biobank's giant genetics database.
They estimated that approximately 1 percent of the data in the database came from individuals with two delta-32 variant copies of the gene. It is important that they calculate that this tiny fraction was 21 percent more likely to die before their 76th birthday, compared to at least a "normal" copy of the gene.
Thankfully, what happens in science often attracts skeptical investigations. Others quickly dived into the statistics to look for similar correlations with both UK Biobank and other nations' data sets and came empty-handed.
So where did Nielsen and his colleagues go wrong?
The reason for the deviation could lie in how the data was collected in the first place.
One way to find out if a person has a specific gene is to simply use a template that gets stuck in a target sequence. These probes do not always work perfectly, which means that some people will incorrectly appear as negative in the database.
By potentially underestimating the number of people with the CCR5 delta-32 receptor, Nielsen risked masking the true effect of the mutation, it seems that there is a difference in mortality statistics. So he asked for the paper to be recalled.
For researchers, huge banks of genetic and medical data collected across the population provide the necessary amount of information needed to discover subtle patterns that delineate healthy ones from unhealthy bodies.  Yet as potentially useful as that statistic is, there are dangers of forgetting that they make many assumptions.
You can see the now canceled essay here.