Researchers at the University of California, San Francisco looked for a genetic explanation, enrolling nearly 30,000 registry volunteers with known immune gene profiles and tracking those who tested positive.
Among 1,428 unvaccinated people who tested positive, those carrying a common variant called HLA-B*15:01 were far more likely to stay completely symptom-free than people without it. Blood drawn years before the pandemic showed that carriers already had memory immune cells primed to recognize a piece of the virus, left over from exposure to ordinary seasonal coronaviruses.
The finding held up in two independent groups of people, which is unusual for a genetic association this specific. It helps explain why some people seemed to dodge the virus's effects entirely while living with someone seriously ill, pointing to prior immunity from common cold coronaviruses as a hidden layer of protection.
Read the original study
Augusto et al., Nature, 2023 · doi.org/10.1038/s41586-023-06331-x
Some immune systems had already met this enemy.
Source
- Augusto, D. G., Murdolo, L. D., Chatzileontiadou, D. S. M., Sabatino, J. J., Yusufali, T., Peyser, N. D., Butcher, X., Kizer, K., Guthrie, K., Murray, V. W., Pae, V., Sarvadhavabhatla, S., Beltran, F., Gill, G. S., Lynch, K. L., Yun, C., Maguire, C. T., Peluso, M. J., Hoh, R., . . . Hollenbach, J. A. (2023). A common allele of HLA is associated with asymptomatic SARS-CoV-2 infection. Nature, 620(7972), 128–136. https://doi.org/10.1038/s41586-023-06331-x