The efficacy of the vaccine is age dependent. Younger people will have stronger, longer lasting protection. The elderly (in this case people over 80) will have weaker, shorter lasting protection and will need to be revaccinated more frequently according to this study.
Also This: “This article is a preprint and has not been certified by peer review [what does this mean?]. It reports new medical research that has yet to be evaluated and so should not be used to guide clinical practice.”
No it does not exactly mean “The efficacy of the vaccine is age dependent ... and will have to be revaccinated more frequently”
it means that in 1/3 of people over 80 this specific “vaccine” is not effective.
I think it means that they should wait until there are studies of other “vaccines” before making a choice and assuming they are protected.
The flu vaccine is the same. There is a more robust vaccine given to those over 65