08-19-2020, 03:38 PM
Since even the earliest cases of COVID-19 were less than a year ago, speculation as to whether immunity wanes after a year or a couple of years is, just that, speculation. Immunity may only last only a short while, or you may get tetanus-like immunity (5 - 10 years) , or you might get polio-like immunity (lifelong). Even if immunity wanes a bit, you may still be protected from life-threatening consequences. But these are the sorts of things we won't know for sure until years from now.
For many of the diseases you cite, we did reach herd immunity through vaccination. Others, which are not transmitted person-to-person, have been dealt with by dealing with the reservoir of disease (mosquitoes for yellow fever, rats and their fleas for the plague, unsafe water for cholera, etc.)
Measels requires herd immunity to stay up because its R0 is about 10, so unless 90+% of people are immune through vaccination, you will get outbreaks, as we saw last year in New York.
BC
For many of the diseases you cite, we did reach herd immunity through vaccination. Others, which are not transmitted person-to-person, have been dealt with by dealing with the reservoir of disease (mosquitoes for yellow fever, rats and their fleas for the plague, unsafe water for cholera, etc.)
Measels requires herd immunity to stay up because its R0 is about 10, so unless 90+% of people are immune through vaccination, you will get outbreaks, as we saw last year in New York.
BC