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Comment by callumprentice | Hacker News Reader

Can anyone point me to a reliable source that explains in layman's terms why one cancels out the other and it's not possible to have both (say) delta and omicron at once.

Somewhat tongue in cheek, but since cancellation seems to be the case, could we not create a version that was 100x more transmissible than omicron but completely benign? Cane toads in Australia aside ;)

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Exponential growth. Lets say that there is one delta infection and one omicron infection in the population. Each delta infection causes two more people to be infected, while each omicron infection causes three more people to be infected.

The growth of a single delta infection: 1 -> 2 -> 4 -> 8 -> 16 -> 32 -> 64

Versus a single omicron infection: 1 -> 3 -> 9 -> 27 -> 81 -> 243 -> 729

Omicron started out as 50% of the cases and over 6 reinfection cycles became 90% of the cases. Delta just can't keep up. These are made up numbers but that is the general idea.

Nod - that explains why omicron grew so quickly but why, in doing so, does delta not persist?

It does persist, all else remaining the same, but since it is so much less infectious it will go extinct if and when anything makes a dent in Omicron. Dents including lockdowns, increased vaccination, changes in public behavior or eventual immunity.

i assume that the immunity you get from having O helps damp down cases of D

To actually answer the question: because immunity from one transfers to the other.

Omicron is basically a self-administering vaccine that is preventing Delta from spreading as easily.

I love this self-administering vaccine as it so elegantly explains the answer to the parent's question.

BUT, it is so elegant that you just provided fuel for the new conspiracy theory of how government forced us to get vaccinated by creating this crazy new variant in a lab that would essentially spread the vaccine without our permission. Just waiting for that to start bubbling up from the fringes ;)

Unfortunately, things don't need to be one way or the other for conspiracy theorists to spin it the way they want to.

> could we not create a version that was 100x more transmissible than omicron but completely benign? Cane toads in Australia aside ;)

You overestimate our abilities to make viruses that do what we want, let alone to make viruses that do what we want and won't evolve into viruses that do what we don't want after being released into the wild.

This is also basically saying "can't we make a transmissible vaccine", and as much as I like vaccine mandates, I think there would be significant ethical issues with that.

A bit of a sidebar this was basically the plot of The Last Ship. With infrastructure of the world crumbling how do you distribute immunity without the manufacturing infrastructure.

So yeah I'd put it in a 'last ditch Hail Mary to save the world' type of plan...

I feel like I recall at least one worm that somebody released that would infect servers, patch the vulnerability that it used to get in, infect other vulnerable servers, then delete itself.

I think it's because Omicron spreads more quickly and confers some immunity towards Delta. So before Delta has had a chance to infect a given person, they've probably already gotten some immunity from Omicron.

Just a no sources comment: you can get confection of the flu and covid or any variant with any other variant at the same time. It's just over time one variant out competes the others because it's more fit.

Dumb question that's been vaguely nagging at me: If a host can have both at the same time, in what sense are they competing? There are plenty of cells to infect in a particular host aren't there?

They're competing to infect the next hosts in the chain. With two present, the one that can get itself passed on more often wins overall.

Ah, so you can contract both viruses but are only likely to pass one on? Do you know why that is?

They have different transmission probabilities. Omicron has far more presence in the upper respiratory tract. It's just a numbers game, they're not competing in any active sense.

In that case I don't understand the "omicron will outcompete other variants" thing I keep reading about. If they don't interact wouldn't the progress of one variant be unaffected by the presence of another?

I think you're correct - if Omicron and Delta provided no cross-immunity, there would be no competition, and they would just continue on their own trajectories as if the other didn't exist.

But, I think that's not actually the case. Omicron infection does provide some immunity against Delta. See this preliminary report from South Africa, for example: https://www.ahri.org/omicron-infection-enhances-neutralising...

I'm not an expert (so take this next part with a very large grain of salt), but I would guess that someone with an active Omicron infection (and so swarming with antibodies) would get the biggest immunity boost against Delta. So if Omicron is everywhere, Delta runs out of infectable hosts. In principle, it could even go extinct - if that were to happen, it wouldn't matter so much if Omicron-induced immunity wanes, there would be no Delta left once the shields are down.

IIRC there was a study showing Omicron antibodies are effective against previous variants, but not vice versa.

[edit] I think this is where I heard that. Feel free to judge for yourself how reliable the source is. https://www.youtube.com/watch?v=PYLbJ0H8zdc

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