Don't be in too big a hurry to put those masks up just yet.
I expect the US is going to see yet another wave of Covid in the next few months. Delta strain.
The estimated R₀ of Delta is somewhere between 5 and 8. So there's just no way we're going to reach herd immunity threshold for this stuff before it shoves out the other strains and becomes the dominant strain circulating in North America. The way it's a
eady done in England.
- You reach herd immunity when the percentage of the population that's immune ≅ (R₀ -1)/R₀.
- Assume optimistically that Delta's R₀ is 5. Then we'll reach herd immunity when we get (5-1)/5 = 4/5 = 80% of the US population immune.
- That is not happening and it's not going to.
- And keeping Delta out isn't an option, it's aeady here.
So we're in for another wave.
Don't be too surprised if there's yet another wave after that.
Sinovac's efficacy rate of roughly 50% means that every country that relies on it is in for a hell of a rough ride. But there's an evolutionary bow shock that affects everybody else, no matter what vaccine they're using.
Consider, for a moment, the following facts:
- An emerging disease, particularly a virus, is under heavy selection pressure to improve at infecting humans. The ones that fail gutter out.
- An RNA virus is genetically unstable by its nature. Covid is less so than most, but it still manages about 25 mutations per year.
- An RNA virus' intrinsic (and minimum) mutation rate is governed by the specific RNA polymerase protein the virus codes for.
- So every human who's down with this stuff is a walking Covid mutation engine, because it mutates precisely when it's replicating in a host.
- If you vaccinate every single susceptible human in a given country with Sinovac, half of them will still remain susceptible anyway.
- So we can, indeed must, expect further adaptive mutation of Covid.
- So Covid will probably grow out new "variants of concern" after Delta has run its course.
Which means we may get hit by yet another wave, after Delta peaks and starts to trough.
