[Question #1627] HEP B

46 months ago
46 months ago
Dear Sirs, 

Six weeks ago I had a potential exposure and I would like to know whether there is any risk for hepatitis and to understand the efficacy of vaccination.
I have been vaccinated, as a child, for hep b  and according to the tests that I received yesterday I am
- hbsag negative 
- anti hbc negative
- while my anti hbs is over 100 miu (107).

I know that it is too soon to obtain a conclusive hbsag testm, which takes 3 months. Though taking into account that the anti hbs is over 100 (meaning that I have been succesfully vaccinated as a child), does that mean that It is 100% certain that I cannot get infected, no matter what? Or is it still possible to become infected, but unlikely.

I have read that the efficay of the vaccine is 95%. Where does this percentage refer to? To the efficay of the vaccine in producing antibodies (succesfuly vaccination); or to the efficacy of the vaccine in protecting a succesfuly vaccinated person from infection, meaining that even a succesfuly vaccinated person with immunity has 5% chances of  becoming infected?

Thank you in advance



Edward W. Hook M.D.
Edward W. Hook M.D.
46 months ago

Welcome to our Forum.  You are asking good questions.  No vaccine is 100% effective for preventing infection but the hepatitis B vaccine is, as you point out, highly effective for preventing infection in exposed persons, making them more than 95% less likely to become infected than unvaccinated persons.  Further, for those who do become infected, the vaccine causes a milder illness with a lower likelihood of both severe infection and chronic hepatitis B.  Thus, when you consider that most people do not have transmissible hepatitis B and that the risk for infection if exposed is in the 1 in 100-1000% range (i.e. considerably less than 1%), vaccination makes the risk for acquisition of hepatitis B in vaccinated persons less than I in 100,000 IF exposed to an infectious partner. 

In your case, your anti-HbsAB level is in the protective range indicating that your childhood vaccine is still leading to relatively high and therefore protective antibody levels.  FYI and not relevant to you but for others who may be reading this, even when a vaccinated person has an antibody level of less than 100 miu, they have some degree of protection form infection.

Given your vaccine status, even if you MAY have been exposed, your risk for infection is very, very low.  I would not be worried if I were you.  EWH

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46 months ago
dear doctor,
one last question.
how long after exposure is the hbsag ante gen test completely conclusive?
thanks
Edward W. Hook M.D.
Edward W. Hook M.D.
46 months ago
Typically, if you had acquired hepatitis B, the HB s AG would be detectable within a month.  EWH
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46 months ago
And how long could seroconversion delay in the worst scenario?
Edward W. Hook M.D.
Edward W. Hook M.D.
46 months ago

Final answer. Hepatitis B antigen can appear in the blood of infected persons as early as five days after acquisition and virtually all infections result in detectable hepatitis B sAg by 30 days.  Certainly if you had not detected antigen by 60 days you could be completely confident that you were not infected.

As this is your third question, as per Forum Guidelines this thread will be closed later today.  Take care.  EWH

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