*There should be no question about stopping breastfeeding*.  The baby
should continue at the breast.  The mother is immune if she has the
antibody, and is passing on antibodies to her baby through her milk,
as well as other sensitized immune factors.  There is no need to wait
or stop until the vaccine to kick in, which it might not do at all.  A
fair number of people do not become immune with the vaccine even after
3 doses (a couple of months apart).

If you really want to be extra careful, the baby could get immune
globulin.

But some information is missing in this picture.  If the father was
infected as a child, and this is a exacerbation of *chronic active
hepatitis*, he is, in fact, *not* infectious.  If the mother was
hepatitis B positive during pregancy, the baby should have received
immune globulin and first immunization at birth.

Jack Newman MD, FRCPC