Was the patient encounter for Hep Vaccine, and then diagnosed with Hep A and B. Chapter one is not my strong point but if you describe the encounter better I will give it a shot; and so will other coders because this is an equivocal scenario.
I have noticed coders will contribute their candor and enjoy rectifying scenarios once another coder has tried and is wrong.
So I would code it as a diagnosis Hep A principal/primary and B secondary, or,
code it as a V code with hep A and hep B listed as additional. So the scenario is encrypted as patient encounter for hep vacc(V code principal), code results are positive for hep A and hep B; but then V codes are used to list encounters for all but disease and injury.
My book doesn't explain how to code hepatits vaccine or virus so it will be interesting to hear a pundit response.