“Melmo Elmo” is an excellent name

So with flu in particular it mutates constantly with old strains becoming less common and new ones we don’t have vaccines for becoming more common each year. That’s why you get regular boosters to get the latest version of the vaccine.

Sadly we can’t predict how it might mutate, and things like flu and covid mutate a lot, so we can’t make a preemptive vaccine.

For viruses that mutate slower (often because they spread slower through populations and/or are very rare), your childhood vaccination is likely to stay effective your whole life.