In terms of cross protection, it depends on many factors. Is the vaccine designed for long-term or short term protection? How closely related are the two different antigens? Are they related enough that your immune system will be unable to distinguish the two (
and assume they are the same)? What is the mutation rate of the antigen?
If you have
a type
B flu, you will NOT have cross protection with type
A. The antigens are too different. However, this year's vaccine contains A/Panama/2007/99 (H3N2) virus, A/New Caledonia/20/99 (H1N1)-like,
and B/Hong Kong/1434/2002.
This year's prevalent flu strain, A/Fujian, is
a mutation of the A/Panama strain. So while it isn't an exact match to the flu vaccine, there is enough similarities to generate some cross-protection. No one knows exactly how much immunity the flu shot will provide against the A/Fujian strain
OK, now to tackle the hepatitis question
If you are vaccinated against
A and B, you won't be immune to C. The vaccine for
Hep A isn't routinely given though unless you are in
a high risk category (or you are in an area of epidemic of
Hep A). The good news is that if you are immune to
Hep B, you won't get
Hep D (since
Hep D can only infect people w/
Hep B)
There is no vaccine for
Hep C. If you are really worried, you can get tested for
Hep C (people at high/intermediate risk are ... if you receive blood/organ before 1992, or you are/were an IV drug abuser, received clotting factors in the 80s, or go on hemodialysis).
To minimize risk of getting
Hep C, don't use products that your infected family member may use that may contain blood (razor, toothbrush, etc). Be careful of tatoo parlors (improper cleaning technique). Most infection of
Hep C in the US is due to IV drug abuse.
If you are truly concer, talk to your physician
Hope I answered your questions
