At birth vaccines (Hepatits B Birth Dose and BCG) were given to B/O Aminah in Hospital A. 2 months later, Aminah brought her baby to take Hexaxim (Dose 1) at KK B. How does the clinic staff trace the past vaccine history of the baby?

As for now, past history of vaccines can be searchable given that the records were done at the same facility. 

Vaccine records are not searchable if they were done at two different places. It is advisable for the clinic staffs to trace the past history of vaccine details via Buku Rekod Kesihatan Bayi dan Kanak-kanak and MySejahtera application of the guardian.