Before we speculate on how Omicron may spread, perhaps we should do a postmortem on Delta? In India, after the big spike of April, the daily new cases dropped way down. In pre-Omicron South Africa, daily new cases were also low. Presumably there are other countries where a Delta boom has died away to a trickle of daily cases. Do we have any understanding of why?
About Omicron, there is speculation that it has been selected to escape vaccines. But my understanding was that vaccines don’t do much to stop the spread anyway, they just protect against severe illness. Is this wrong? Or is the idea that people who do fall ill, produce enough extra virus, that there is selection pressure to produce a virus which evades even the protection against illness?
I’ll also remark that natural immunity is likely to be more robust than mRNA-vaccine-derived immunity, since the latter gives you antibodies just against the spike protein, while natural immunity will produce antibodies against other components of the virus too.
“Another possibility, still speculative but discussed by many scientists in recent days, is that omicron evolved over many months within an immunocompromised patient with a protracted infection. In a patient treated with therapeutics such as monoclonal antibodies or convalescent sera, a viral strain that can survive the assault can potentially amass a host of mutations. Such cases have been documented, but they are not known to have led to outbreaks in the general population.”
Before we speculate on how Omicron may spread, perhaps we should do a postmortem on Delta? In India, after the big spike of April, the daily new cases dropped way down. In pre-Omicron South Africa, daily new cases were also low. Presumably there are other countries where a Delta boom has died away to a trickle of daily cases. Do we have any understanding of why?
About Omicron, there is speculation that it has been selected to escape vaccines. But my understanding was that vaccines don’t do much to stop the spread anyway, they just protect against severe illness. Is this wrong? Or is the idea that people who do fall ill, produce enough extra virus, that there is selection pressure to produce a virus which evades even the protection against illness?
I’ll also remark that natural immunity is likely to be more robust than mRNA-vaccine-derived immunity, since the latter gives you antibodies just against the spike protein, while natural immunity will produce antibodies against other components of the virus too.
It seems that Omicron may have mutated over time within a single immunocompromised host, so it’s not clear to me how natural selection applies.
Sources?
“Another possibility, still speculative but discussed by many scientists in recent days, is that omicron evolved over many months within an immunocompromised patient with a protracted infection. In a patient treated with therapeutics such as monoclonal antibodies or convalescent sera, a viral strain that can survive the assault can potentially amass a host of mutations. Such cases have been documented, but they are not known to have led to outbreaks in the general population.”
Source:
https://www.washingtonpost.com/health/2021/11/29/how-bad-is-omicron-variant/
This does seem to be a recurring theme—very slow mutation for the most part, and lots of new mutations occurring in immunocompromised “supermutators”.