It probably cannot be done. This more than likely works in a similar way to the insurance information, in that for an entry to stop appearing in the list all traces of it in patient charts must be removed. We have that problem. Having 10 BCBS entries with different addresses or phone numbers causes this. In your case, I would imagine that any chart with that information in it causes the field to be populated. If you remove that info then you would be changing the information about the previous immunization, which would be a huge "no-no".