If there's autoimmune issues that pop up when the scale goes from tens of thousands to hundreds of millions, I'll know about it ahead of time and be able to take the appropriate action, such as choosing a non-mRNA vaccine such as the adenovirus type from Astrazeneca.
Vaccines are not 100% effective but they don't have to be. The goal here is to reduce transmission in the population to a level where the virus can no longer spread. That is only possible if enough people take the vaccine and healthy people should absolutely be in the front of that line.
This is not a purely personal choice. You have to understand that by deciding not to immunize yourself you are making a decision for everyone else.
https://www.cdc.gov/vaccinesafety/concerns/concerns-history....
On the other hand, if you want to read about how software works when it actually matters, "space shuttle coding style" is fascinating.