It’s worth reading the full text yourself: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9839603/ . As usual, the study provides much more information than the linked-to summary.

In this study, the authors analyzed 4 time periods, the first 2 of which were before vaccines were even available. For different age groups, the increase was identified in all 4 periods:

https://www.ncbi.nlm.nih.gov/core/lw/2.0/html/tileshop_pmc/t...