There is a strange bump around 2 months on graphs of sever illnesses and infection rates at 2 months [1]. Can anyone explain or point in the direction where it is explain the paper?

Second, Cox models for vaccine effectiveness(Infection and Sever illnesses) show decline around 6-7 months, which is knows well now. But what part of these decline attributed to effect of the vaccine vs emergence of a new variants? In other works, what would the curve look like, if there was no Delta & Omicron or if they appeared very shortly after the first variant? It is being said that booster does not prevent Omicron spread, thus maybe declining effectiveness in infection prevention can be explained partially by the new variant.

And lastly: Data sharing The data that support the findings of this study are available from Lombardy Regional Health Service, but restrictions apply to the availability of these data ... Data are, however, available from the Lombardy Regional Health Service upon reasonable request.

It is upsetting, that data is not readily available, the cohorts are huge, thus the possibility of deanonymization can be excluded.

UPDATE: It looks like Omicron was detected in Italy on Nov 28, 2021, so a month after the end of the study's follow up ended (Oct 20, 2021). Is it possible that it had been already circulating widely enough to affect survival curves before it was officially reported in Italy?

Also, were lockdown measures used as a covariate? It is hard to find time time of lockdown measures in Italy and specifically in Lombardy and it would not be possible to superimpose it on survival curves, because survival curves are relative to a timeline measure in time entering the study, but I seems plausible to me that similar demographic received vaccines and was affected by changes in lockdowns around the same time. E.g. most of the kids of a specific age got vaccine at the same time and X months later schools reopened, so some of the bumps on the curve can be explained by it.

[1] https://els-jbs-prod-cdn.jbs.elsevierhealth.com/cms/attachme...

[2] https://els-jbs-prod-cdn.jbs.elsevierhealth.com/cms/attachme...

Probably the only interesting aspect of this, is how frequently elderly and those at risk should get booster shots.

And booster shots might not help that much with stopping infections, but will help in keeping people out of hospitals.

Very similar to how the vaccine for seasonal influenza works.

https://edition.cnn.com/2021/12/16/health/flu-vaccine-mismat...