Why Delta Might Be a Good Variant

I’m no epidemiologist, but it occurred to me that there might be a silver lining with the COVID-19 Delta variant.

  1. Delta is explosively contagious, with an R0 between 6 and 9. This means that the average infected individual is expected to transmit Delta to 6 and 9 additional people (versus 2.5 for COVID-19).
  2. This means that it just rips through populations. Because it can be transmitted by the vaccinated, it can travel deeper across the population as well.
  3. But so far is has not been found to be more lethal than the original, except to the extent that it crushes hospital capacity with its surge.
  4. Think about the virus’ evolutionary goals. It doesn’t actually care whether people live or die – the variant that spreads best dominates. If Delta manages that, while letting the vaccinated largely be unharmed, then it could become the pandemic’s endpoint.
  5. Why? Delta might crowd out new variants if it gets around and becomes the primary endemic version. To defeat Delta and take its dominant position, the next variant would have to be even better at spreading.
  6. Of course that is possible, but if Delta already can be spread by the vaccinated, it’s possible that is has already maximized the population growth prospects for this kind of virus in humans. The vaccinated can carry a Delta population in their nose without realizing it.
  7. Ironically, if any current vaccine were perfect, it would leave an attack surface for the next variant – conquer the vaccine. Perhaps the optimal vaccine simply allows us to live with the Coronavirus and welcome it to the family of standard household colds?
  8. And so perhaps Delta has evolved to be well suited to our current vaccines, able to maximize its reproduction. If we are lucky, it will crowd out any more lethal strains – marking the beginning of the end of the pandemic. There’s some indication that this might be happening, as Lambda has been present for some time, but has yet to grow in the US to extent that Delta has.
  9. This all assumes that vaccination efforts eventually meet with success and cover the overwhelming majority of the human population.

This could be wishful thinking – new variants will either validate or make a mockery of it soon. But the explosive growth and subsequent subsidence in COVID Delta cases in the UK and India give me room for hope!

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