The APOE4 gene is a gene that affects the inheritability of Alzheimer's disease. If you inherit two copies of this gene, one from your mother and one from your father, you are 14 times more likely to develop Alzheimer's, compared to others with two copies of the APOE3 gene. A study recently done in England looked at 622 individuals who tested positive for Covid-19, and in this study, 37 of those people had two copies of the APOE4 gene. I know, this does not sound like that many people, but if you increase the sample size, this is 410 out of every 100,000 people, compared to those without the two copies of the APOE4 gene, coming in at only 179 out of every 100,000 people. Further studies are currently being done to test how having two copies of the APOE4 increase vulnerability of contracting coronavirus, but from what has been done so far, I think there is good evidence to connect this gene with increased risk of getting Covid-19. I think one factor that these researchers need to consider however, is the age of the people testing positive for Covid-19 and having the two copies of the APOE4 gene. Typically, Alzheimer's susceptibility increases with age, and so does susceptibility to coronavirus, so age needs to be a factor that is considered before we can accept the idea that two copies of the APOE4 gene increase risk of Covid-19.