Almost certainly vaccine immunity is more robust than asymptomatic infections (especially those that rely on the innate immune response rather than adaptive immune response). Asymptomatic infections (especially in the young) are extremely common and possibly in the majority for those under 30.
Those only measured patients who suffered acute symptoms. Those are unlikely to represent even a bare majority of infections although it's quite difficult to get accurate data for asymptomatic infections.
https://www.nature.com/articles/s41586-021-03696-9
"only 10% had been hospitalized"
I look forward to your citation of relevant peer-reviewed longitudinal studies.
Even more interesting from a medical point of view, what mechanism do you propose for developing long term immunity, where the innate immune system rapidly controls infection?
The point I made was that vaccination is not more robust than being infected, or at least dont assume it is without solid evidence to support it.
The whole point is that the adaptive immune system doesn't really ramp up for many days up to weeks, while viral load typically peaks at 3-5 days. That's why the second shot is typically delayed for the MRNA vaccines. A young asymptomatic carrier with a strong innate response who recovers early is unlikely to develop a significant adaptive immune response (e.g. test positive on an antibody serology) thus they are also then very unlikely to develop durable immunity.
"Longitudinal analysis shows durable and broad immune memory after SARS-CoV-2 infection with persisting antibody responses and memory B and T cells".
Is that good enough for you?
So unfortunately since I specifically and repeatedly referred to asymptomatic cases, which are relatively common in those under 30, it is not good enough.
If I could edit my original post to <B>BOLD</B> asymptomatic even more, I would, since I highly doubt you're going to find many studies on that group.
The sample size is very small and they list other limitations to their findings, but:
"In conclusion, despite concerns of waning immunity, appropriate immunoassays can detect antibodies against SARS-CoV-2 at 8 months after infection in most asymptomatic or mildly symptomatic persons."
However, from my very first post "vaccine immunity is more robust than asymptomatic infections"... and detectable antibodies is a far cry (orders of magnitude) from neutralizing antibody levels, which are not uncommon even 8 months out in healthy vaccinated youth.