I have an uncanny situation with one of my WIPs. It's set in 2055 and the MC's a cloned Neandertal. Due to his immune system having missed out on the last 40,000 years of evolution he's susceptible to some modern pathogens. As he's been vaccinated against pretty much everything that has a vaccine (due to this problem), it's mostly cold viruses and harmless (to modern humans) bacteria that he's potentially susceptible to, and it's random which ones don't make him ill or just give him a cold, and which ones make him severely ill. I based this on research into the evolution of disease causing organisms. In the story he ends up in intensive care with pneumonia and sepsis from an illness that started off as a fever and a cough. It's a cold virus that makes him ill, plus a secondary infection with a harmless-to-modern-humans bacteria. Prompt treatment with 2055 medicine means he survives without long term physical ill effects, though it affects him psychologically. And that was all written before COVID-19 was a thing.
I shouldn't be too surprised at the similarity to COVID-19 because I did my research, and part of that was learning that cold viruses can cause some chimpanzees to get potentially fatal pneumonia while other chimps just get a cold. That is also extremely similar to COVID-19 in humans, and it's because that's what happens when things first jump the species barrier and a population has no prior exposure (natural selection, over time, will result in genes that cause increased susceptibility to be lost from the gene pool, and at the same time the pathogen adapts to survive better in the new species - killing your host or making the host severely ill reduces the chances of the pathogen spreading, especially for viruses as they can't breed outside of living cells - mild illness and symptomless spreading is favoured by natural selection.)
I've only made small changes in the story, which is because the similarity of the MC's illness to COVID-19 would not go unremarked upon by the doctors treating him. So it gets mentioned, but doesn't change the plot. But my MC won't get COVID-19 because he would've been vaccinated against it.
Making comparisons with COVID-19 does bring it home how vulnerable the MC is to infection by modern pathogens, which is a good thing as the theme of the story is ethics, i.e. how unethical it would be to clone a Neandertal. And it makes his surrogate parents/scientists who cloned him look bad. They're not bad people and they look after him well, but they didn't think things through. It's very hard not to quote Jurassic Park... "Your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should." - it's so applicable. But as I can't quote verbatum from other writers without permission, it will have to remain unsaid. I'm sure readers will think it.