One problem with maintaining a good immune response while isolated: your system NEEDS to be exposed to stuff regularly or it starts to regress. That's part of the problem with people becoming so germaphobic - we have become LESS resistant to diseases and pathogens. If you are a healthy person with no underlying immune-compromising conditions, you are doing yourself a disservice by trying to protect yourself from a disease that, as data is starting to show, not that dangerous (to quote one such study: "large number of infections; small number of deaths") Travel bans and quarantines were a good idea in the beginning, because no one knew (thanks to one country's lack of transparency) just how serious this brand new disease was going to be. No one knew at first how it was transmitted, where it came from, or anything else about it. We do know NOW that it started a lot earlier than anyone realized- as early as November in China. There were something like 3 flights a day coming from Wuhan to America daily until the travel ban was ordered. The Kung Flu was already here and spreading rapidly, but people probably just figured they had the flu and didn't even bother to go to the doctor since we already know how to deal with the flu. Some never even knew they had it. These people are already immune and don't know it; they are living in fear of getting this dreaded disease needlessly.
Before you all start jumping down my throat: Yes, I am fully aware that a lot of people have died. But the data is showing that the percentages are not any higher than the flu. The numbers in places like NYC are higher in part because people were being sent to nursing homes from the hospitals instead of places like the Navy hospital ship (which spent 3 weeks in NYC and finally left after being given only one patient to care for: a motorcycle accident). Nursing homes are, by their very nature, full of people with compromised immune systems, so of course they died like flies.
eta: I found out that the hospital ship had more patients to care for- but it was still only 179 patients; nowhere near their capacity
Most people don't worry about getting the flu, in fact about 50% of the population doesn't bother with getting a flu shot and a lot of the ones that do get one are only doing so because they are required to get one by their place of employment (my DH was one before he retired)
Take a look at what's happening in Sweden. They are approximately the same size as Michigan, same population. Michigan instituted a truly draconian lockdown, Sweden didn't do anything but advise people to practice social distancing (and it allowed citizens to decide what that meant) and suggested that the elderly take extra precautions. The result? Both have had very similar numbers of hospitalizations and deaths, but antibody testing is showing that Sweden is approaching "herd immunity", which means that even if the disease mutates, they won't have the spikes of infection and death. Michigan does not have herd immunity because they haven't been exposed.
This disease isn't going anywhere. You can't hide in your houses and hope it just goes away. A vaccine is probably years away, and if people try to wait until then to open society, there probably won't be a need for it because everyone will have died from starvation, other diseases or life-threatening conditions, suicide, domestic violence and abuse- all very real dangers of extended isolation.