How effective is the HepB vaccine?


I was diagnosed with chronic hepatitis B about two weeks ago. I got the HepB vaccine when I was 9. I donated blood until 2017 and was tested for HepB regularly until then. I never had a positive test until 2023, when I restarted blood donations.

I have come to terms with the fact that I will probably never figure out where or how I got HepB. But I am very concerned for my partner.

The doctor said if he is vaccinated the risk of transmission is “practically 0.” But I am vaccinated, and I somehow got it. Does anyone know what the vaccine’s efficacy rate is?

Dear @Holly ,

Vaccination for HBV is highly effective but no vaccine is 100% effective in preventing disease. There are always factors which can influence this in individuals.

There is a significant breakthrough following vaccination for those individuals who were infected during birth (from their mother -we call this maternal transfer). This breakthrough rate can vary from 5-30% depending on the ethnic background of the population.

However, your case is unusual since there has been a very long delay between vaccination and the onset of diagnosis. This is not typical for viral breakthrough following birth dose vaccination after maternal transfer.

I would consider that your partner is safe with his vaccination but if you are concerned you can have him consult with his doctor to see if he still has protective levels of antibodies to the HBV surface antigen (HBsAg).

In your case, your positive blood test should have triggered an evaluation of the level of viral replication in your blood (HBV DNA) as well as how your liver is functioning. These tests will be important to decide how to proceed.

Best of luck…

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Dear @holly,

Welcome to the forum and so sorry to hear about your experiences. The real efficacy rate is variable, as mentioned by @availlant. Antibody levels can also decrease with age (though I’m not sure how much this correlates with protection, because antibodies can be quickly generated by memory B cells)

There is a bit more information about this on the Hepatitis B foundation website: Hepatitis B Foundation: Vaccine Non-Responders

Hope this helps,