It's probably based on the fact that this virus is a coronavirus, and there are 4 other coronaviruses that are endemic, seasonal and to which we do not gain a l

It's probably based on the fact that this virus is a coronavirus, and there are 4 other coronaviruses that are endemic, seasonal and to which we do not gain a lasting immunity after infection. Given that the probable mortality rate for people over 70 is 10% or 15% for this virus, and that any vaccine will not be anywhere near 100% effective for 100% of the population, not living in a densely packed big city is entirely rational.