In the case of vaccine efficacy vs. severe disease, it is
the fact that both vaccination status and risk of severe
disease are systematically higher in the older age group
that makes overall efficacy numbers if estimated without
stratifying by age misleading, producing a paradoxical
result that the overall efficacy (67.5%) is much lower
than the efficacy for either of the age groups (91.8% and
85.2%).
Thanks for sharing this analysis. I scanned through it and it seems reasonable to me. I don't think anyone actually thinks natural immunity is 7 times as effective as vaccine immunity, as the numbers suggest might suggest without deeper or more thorough analysis.
As far as I can tell, the analysis you link also continues to support the notion that natural immunity works wonderfully well, on par with or better than vaccine immunity as far as we can tell.
