He had HepB at 1 day of age at 8 weeks he had HepB, DTaP, Hib, IPV, and PCV.

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He had HepB at 1 day of age at 8 weeks he had HepB, DTaP, Hib, IPV, and PCV.

This is a comma splice that can be fixed by changing the comma after HepB to a semicolon.