Why the Delta variant’s R0 of 6-9 means that stopping it (bringing Re to below 1) with just vaccination is unlikely:
or, for those who prefer it in <280 character chunks:
The other conclusion is that getting unvaccinated people vaccinated helps reduce Re more than vaccinated people getting boosters. Of course, it may be that the remaining unvaccinated people have a lot of hard-line refusers, so getting them vaccinated is unlikely.
Of course, the policy implication is that we then have a choice between:
- Trying to bring Re below 1 with vaccination plus additional measures like mask and social distancing requirements, restrictions on indoor gatherings and travel, etc., which people are tired of and which have negative implications on education and other things, or
- Giving up on trying to control COVID-19 and let the vaccinated people hope that the vaccines’ reduction in getting COVID-19 and reduction of bad outcomes if one gets COVID-19 works for them, and hoping that the overloading of hospitals with mostly-unvaccinated COVID-19 patients is only temporary until COVID-19 has run through the unvaccinated population.