COVID-19 can have a variety of effects on the human body, ranging from no symptoms at all to death. Researchers have been investigating what factors such as demographics, pre-existing conditions, vaccination status, and genetics, may contribute to the severity of COVID-19 symptoms.
Researchers already know that older people and unvaccinated people are more likely to have complications. According to August data from the US Centers for Disease Control and Prevention, those unvaccinated and over the age of 50 were 12 times as likely to die than those who had received two or more booster shots.
Pre-existing conditions can have a significant impact on the symptoms COVID-19 can cause. For all ages, conditions like heart disease, kidney disease, chronic obstructive pulmonary disease, diabetes, and obesity can exacerbate COVID-19 symptoms. Cancer patients on immunosuppressants, however, are particularly vulnerable. Getting infected may cause a cytokine storm. In AP Bio, we learned that if a pathogen has managed to get past the barrier defenses, macrophages secrete cytokines as part of the innate cellular defense. Cytokines then attract other phagocytes called dendritic cells, as well as smaller phagocytes called neutrophils to digest pathogens and dead cell debris. A cytokine storm is harmful as it can trigger inflammation that damages organs and tissues. 
Scientists have also found that certain genes may predispose individuals to be more susceptible to COVID-19. Studies have shown that some genes from Neanderthals could protect against COVID-19, while other genes could raise the risk of developing severe symptoms. Additionally, scientists discovered that people with variations in the gene called toll-like receptor 7 (TLR7) are 5.3 times more likely to have severe symptoms from COVID-19. Proteins produced from this gene are involved with interferons to alert other cells to raise anti-viral defenses when a virus has invaded. Interferons essentially interfere with the virus. Conversely, having variations in another gene called TYK2 can protect against infection. TYK2 is involved with producing interferons. However, there is a genetic trade-off. Although having more interferons can help fight COVID-19, having more interferons when there is no infection may cause the immune system to attack its own body. Therefore, variations in TYK2 may also increase the chance of developing autoimmune diseases like lupus.
Even with all this research, scientists can not determine the risk that one individual has of having complications with COVID-19. The only factor we can control is our own habits. We should continue to wash our hands, wear masks in crowded spaces, and stay up-to-date with vaccinations. I thought this topic was very interesting because many of us at school do not perceive COVID-19 to be a serious disease anymore. However, we should remain vigilant in preventing the spread of SARS-CoV-2 and other viruses as there are others outside our community that are vulnerable.
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