A previous infection with any variant seems to give immunity against serious illness from other variants.
A previous infection with another variant does not necessarily give immunity against omicron, otherwise there would be no reinfections.
Omicron does not appear to be as severe but you are jumping to conclusions again.
Coronavirus family include common cold, for which there has never been a vaccine. SARS-Cov-2 appears to be going the same way as common cold and will and become a 'background' illness that everyone just learns to lives with, and maybe only kills or causes complications in the already very ill or immuno-suppressed.
and again.
Quote from your link..
'While the inclusion of reinfections means the case-fatality risk – the proportion of people reported to be diagnosed with Covid who go on to die – will fall, Prof Sir David Spiegelhalter, a statistician at the University of Cambridge, cautioned the measure remains problematic'
Fuller quote
"While the inclusion of reinfections means the case-fatality risk – the proportion of people reported to be diagnosed with Covid who go on to die – will fall, Prof Sir David Spiegelhalter, a statistician at the University of Cambridge, cautioned the measure remains problematic.
“We have always known that the daily number of reported cases was a substantial undercount of the actual number of infections – the ONS Covid Infection Survey shows that we have to at least double the daily count,” he said.
“Including reinfections will be an improvement, and will reduce the apparent case-fatality rate, but nobody should have taken this very seriously anyway. The case-fatality ratio is inevitably an overestimate of what is the better measure – the infection fatality ratio, ie the proportion of those who are infected who die, whether or not they become confirmed cases.”
https://www.channel4.com/news/covid-reinfections-now-included-in-government-daily-figuresEdi added Channel 4 link