I seem to remember that if you have had the jab before protection might last longer than previously thought
See my thread on the Health Branch. Yellow fever vaccination booster not needed, says WHO, including the caveat that this does not change the legal requirement for a cert if a country wants to impose that.
There are two serious problems that occur more often in people over 60. I won't burden you with the whole medical rigmarole, just some statements from the CDC
One is called YEL-AND
>The onset of illness for documented cases is 3–28 days after vaccination, and almost all cases were in first-time vaccine recipients. YEL-AND is rarely fatal
The other is YEL-AVD and it is more serious
> YEL-AVD appears to occur after the first dose of yellow fever vaccine, rather than with booster doses.
And, for travelers over age 60
>The risk of YEL-AND and YEL-AVD is also increased in this age group, at 1.8 and 1.4 per 100,000 doses, respectively, compared with 0.8 and 0.4 per 100,000 for all vaccine recipients. Given that YEL-AND and YEL-AVD are seen almost exclusively in primary vaccine recipients, more caution should be exercised with older travelers who may be receiving yellow fever vaccine for the first time.

