Since its emergence in late 2019, SARS-CoV-2 has killed nearly 7 million people. But at the same time, many infections, in particular in children and young adults, are asymptomatic with rapid viral clearance from the body. It remains unclear why many individuals are able to successfully clear infection without major complications while others develop severe disease, even without known risk factors for severe COVID-19 outcomes.

Now, a new study involving nearly 30,000 individuals has found that variation in the human leukocyte antigen (HLA) loci may underlie processes mediating asymptomatic infection. The findings were reported in the July 19, 2023, online edition of Nature.