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Comment by wrycoder | Hacker News Reader

I can understand how previous infection can confer immunity, especially since the immune response is built against live virus, not just spike protein.

What I don’t understand is how vaccination and boosting using an mRNA vaccine that contains only spike protein from the original SARS2, and which is almost completely evaded by the BA.4 and BA.5 variants, can confer protection against severe illnesses caused by those variants.

What is the biochemical process that provides that protection?

EDIT: Is this protection just a happy mantra, or is it actually that there is no protection against the new variants, but the intensity of the disease from them is far less than from the original variant (and our treatment is getting better)?

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There is protection against the new variants. The human immune system has different levels of protection, and these mRNA vaccines seem particularly effective at triggering one of the most flexible, long-term forms -- cellular immunity.

At a very high level, this is the explanation: the spike protein in Omicron has many differences from the vaccine strain spike, but it's still largely the same protein. The immune system is chopping up the protein into chunks, and T- and B-Cells are specializing to recognize those chunks. This kind of immune response (the "cellular immune response") is slower to ramp up than the antibody response that many people have fixated on, but it's a much more robust defense mechanism; B- and T-Cells are very good at providing generalized antigen recognition. There have been at least 2-3 papers I'm aware of where labs have directly demonstrated that vaccinated people are producing robust immune responses to Omicron proteins.

I'd have to dig these up again, and they're not exactly comprehensible by non-specialists, but the executive summary is that we have laboratory and clinical and epidemiological data that the vaccines are still very effective against severe disease.

What the vaccines don't do anymore, is protect against infection. That was probably never a realistic goal for a respiratory virus, but it's definitely not practical with a vaccine that produces antibodies that target a very old spike protein.

If you have a link, I’d be interested in reading the paper!

Here's one from Cell -- as I said, it's very technical, but the TL;DR is that 84% of CD4+ and 85% of CD8+ memory T cell responses to the Omicron spike protein are preserved, compared to an average of 90% and 87% respectively for the other variants:

https://www.sciencedirect.com/science/article/pii/S009286742...

Here's another:

https://www.nature.com/articles/s41586-022-04460-3

> Between 70% and 80% of the CD4+ and CD8+ T cell response to spike was maintained across study groups. Moreover, the magnitude of Omicron cross-reactive T cells was similar for Beta (B.1.351) and Delta (B.1.617.2) variants, despite Omicron harbouring considerably more mutations. In patients who were hospitalized with Omicron infections (n = 19), there were comparable T cell responses to ancestral spike, nucleocapsid and membrane proteins to those in patients hospitalized in previous waves dominated by the ancestral, Beta or Delta variants (n = 49). Thus, despite extensive mutations and reduced susceptibility to neutralizing antibodies of Omicron, the majority of T cell responses induced by vaccination or infection cross-recognize the variant.

I may have read a third, but I can't find it easily, and these two should be more than enough to back up what I wrote / get you started.

One theory I have heard to explain this is that the vaccine is simply suppressing immune response, which helps prevent the cytokine storm that led to severe disease. Of course, this might also make infection more likely, which may explain why so many governments have stopped publishing the case rate breakdowns by vax status.

It makes a kind of intuitive sense: if you make your own body produce some key portion of the virus, maybe your immune system gets tricked into thinking it's not such a big issue?

> the vaccine is simply suppressing immune response, which helps prevent the cytokine storm that led to severe disease.

"Response" is many different things. The vaccine boosts response b/c you have antibodies, so it's much less likely that your body has to do a hail mary las ditch (cytok storm).

> why so many governments have stopped publishing the case rate breakdowns by vax status.

But there's enough data out there to have a clear picture: vaccines or previous infections won't protect you from being infected by the recent strains (BA.2.75, BA.5, etc) but will protect you from severe disease or dying. Maybe it can be improved by nasal vaccines (what happened to those?) but who knows...

> It makes a kind of intuitive sense: if you make your own body produce some key portion of the virus, maybe your immune system gets tricked into thinking it's not such a big issue?

This one is completely off the mark. For starters, not all vaccines have your "body produce part of the virus", yet all help to prevent severe cases and death.

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