How to standardize vaccination age and age groups

[yongqunh]

There are likely different ways to standardize vaccination age, for example, in CDC:
https://www.cdc.gov/vaccines/vpd/vaccines-age.html
https://www.cdc.gov/vaccines/parents/by-age/index.html
https://www.cdc.gov/vaccines/schedules/hcp/imz/child-adolescent.html
They provide different ways to represent vaccination age groups.

However, these age groups appear quite complicated. Is there a more standardized and likely simpler way to group ages? Are vacciantion age groups different from age groups for other studies?

[yongqunh]

As shown here:
https://ieeexplore.ieee.org/abstract/document/6416855
"The human age is classified into four categories as Child (0-12 years), Adolescence (13-18 years), Adult (19-59 years) and Senior Adult (60 years and above) which is discussed in the paper."