This, and the posts from Indah, are models of calm and reason.
See also
Herd immunity - APIC where it says:
When can we expect herd immunity for COVID-19?
COVID-19 is a very contagious disease. A large percentage of the population will need to be immune against the disease (through infection or vaccination) before herd immunity will be achieved. It is not known when that will happen, but it will depend on how many people get vaccinated.
See also
Dissecting the indirect effects caused by vaccines into the basic elements, written before Covid-19, where it says:
High and maintained vaccine effectiveness
Good vaccine effectiveness is crucial in producing a positive indirect effect or good herd protection from a vaccination program.
2 Vaccine
effectiveness is the real-life measurement of a vaccine's ability to protect against infection. This is different from vaccine
efficacy, which is the capacity of a vaccine to provide protection in a controlled environment like clinical trials.
14 Vaccine effectiveness will vary between regions and different (sub)populations,
6 and should therefore be taken into account when evaluating the positive indirect effect of a vaccine on a given population. Since vaccines are almost never 100% effective, the critical vaccination coverage level required to protect the population must necessarily increase.
6,14
The fundamental ideas of herd immunity are not new:
“Herd Immunity”: A Rough Guide. If you dig into the math, there is a relationship between the required vaccination coverage level, Vsub-c, the R-naught (infectionness) of the virus, and effectiveness of the vaccine. If R-naught is 4 (a high estimate for Covid-19), then Vsub-c is 75%, for E=100%. But if E=90%, then Vsub-c goes up to 83%, and if E=75%, then Vsub-c goes up to 100%. So for an infectious virus (R-naught = 4) with a vaccine that is only 75% effective, you need 100% of the population vaccinated to get to herd immunity. The low estimate for the R-naught of Covid-19 is 1.9, in which case an E of only 60% will still provide herd immunity even if only 80% of the population is vaccinated. Those are all bounds based on simple models, but the point is.....you really do need to try and most of your population vaccinated, given the way Covid-19 works and given the effectiveness of our vaccines.