There is some evidence that contracting the disease does not necessarily mean immunity. Additionally as I mentioned in another reply there is some evidence that the vaccine can help with long-term conditions of the disease.
You'll need to cite that evidence in a way that stands up to the idea that it clearly acts as a counterargument to the idea of there being a need for caution about getting the vax at that stage. Given the severity of known immediate side effects upon getting it for people who already had COVID, that alone is a reason to want to know it is gaining you anything.