Should there be a gap between two vaccines?

Q: I have a year old son. He was given the chicken pox vaccine a few days back. Now, the doctor has called us to give him the hepatitis vaccine. I have read somewhere that there should be a gap of atleast one month between each vaccine. Is it alright to give the hepatitis vaccine so soon?

A:It would have been preferable to give both the vaccines simultaneously, at different sites or have an interval of four weeks between the two.