Certain individuals seem to possess a unique ability to resist contracting COVID-19 even when exposed to the virus. Researchers have been intrigued by these cases and have been working diligently to find what contributes to this immunity.
A major area of investigation involves the immune system's response-- particularly the role of T cells, which are a type of immune cell that play a crucial role in the elimination of infected cells. Recent studies, a prominent one being the collaborative study led by Jill Hollenbach's team and researchers from La Trobe University, suggests that prior exposure to similar coronaviruses might be responsible for this resistance. These T-cells could then swiftly identify and defend against the virus, leading to a much better immune response, in turn providing a plausible explanation for why some people seem more resistant to COVID-19, even in the absence of prior infection.
Universityofcalifornia.edu states about Jill Hollenbach’s study, “They recruited nearly 30,000 people who were also in the bone marrow registry and tracked through the first year of the pandemic. At that time, vaccines were not yet available, and many people were undergoing routine COVID testing for work or whenever they were potentially exposed.” This gives a rough idea of the methodology of the study, and its scope. Tracking these individuals over a year during which vaccines were not yet available, provides the opportunity to understand the natural course of COVID-19. Universityofcalifornia.edu then states this about the study and its results:
“ Researchers identified 1,428 unvaccinated donors who tested positive between February 2020 and the end of April 2021, before the vaccines were widely available and when it still took many days to get back test results. Of these, 136 individuals remained asymptomatic for at least two weeks before and after testing positive. Only one of the HLA variants -- HLA-B*15:01 -- had a strong association with asymptomatic COVID-19 infection, and this was reproduced in two independent cohorts. Risk factors for severe COVID-19, like being older, overweight and having chronic diseases like diabetes did not appear to play a role in who remained asymptomatic.” These findings show how genetics seem to be a vital factor in COVID-19 due to the presence of a particular genetic variant, HLA-B*15:01. The gene was strongly associated with the ability to remain asymptomatic after contracting COVID-19, suggesting that certain genetic factors play a significant role in determining whether an individual will show symptoms or remain symptomless even while infected.
Overall, Jill Hollenbach’s study sheds light on the critical role of genetics in COVID-19 and potentially many other viruses as well. These findings underscore the complexity of individual responses to the virus and have implications for understanding immunity and future vaccine development.