C++ :: Function Call That Moves Entity From One Vector To Another

Ok so I have a function call that moves an Entity from one vector to another, and if one doesn't exist then it creates one and moves it:

std::vector<std::unique_ptr<Entity>> ActiveEntities;
std::vector<std::unique_ptr<Entity>> EntityPool;

// Creates a generic entity in the entity pool
void EntityManager::CreateEntity() {

[Code] .....

In this case it checks the entity pool for an entity, if one exists it moves it to the active entities and then returns the unique id, if one doesn't exist it creates one then calls itself to run the check again to verify and move the new entity.

My question is, is this a valid form of recursion since it only incurs a single loop of recursion, or should I reform the entire system to work differently? If so, how do you set this up in a way that does not cause recursion?