Final answer:
After hepatitis B vaccination, an immunocompetent patient is expected to produce IgG antibodies for long-term immunity, with IgM antibodies appearing first but then class-switching to IgG.
Step-by-step explanation:
The expected serological response in an immunocompetent patient who has been vaccinated for hepatitis B is primarily the presence of IgG antibodies. Upon vaccination, the patient's immune system generates an initial wave of IgM antibodies, followed by a class switch to produce IgG antibodies. IgG is the main antibody of secondary responses, involved in long-term immunity, and is a monomeric antibody that helps to clear pathogens from the blood. Therefore, the correct answer is B) IgG only.