Recently a black box warning about Hep B reactivation has been mandated on packaging for DAA medications in the USA by the FDA.
There have been very few cases and it would be reasonable to say it’s something of a storm in a teacup.
Here’s a quick cooks tour of Hep B.
Hep B is a DNA virus that can’t be cured by drugs. That’s because it can form ccDNA – covalently closed DNA – which is like an inactive sleeper form that can reactivate.
We have 4 basic tests:
1) Hep B surface antibodies
2) Hep B core antibodies
3) Hep B Surface Antigen
4) Hep B DNA PCR
Antibodies are immune fighter bits produced by a person.
The surface antigen is part of the virus and is targeted by surface antibody.
The core antigen is part of the virus and is targeted by core antibody
The Hep B DNA is the genetic code (Hep C uses RNA for it’s genetic code)
Somebody who has never been infected has no 1, 2, 3 or 4
Somebody who has been immunised has surface antibody only. The immunisation is surface antigen fragments which lead to the development of these antibodies. Because the core antigens and DNA are missing the immunisation can not produce core antibodies OR infection.
Somebody who has acute infection with Hep B has surface antigen and PCR DNA viral load to start with. The Surface antigen is part of the virus. The DNA is part of the virus so unlike Hep C we have two tests that count viral bits.
Almost all adults (90%) with acute Hep B clear the virus naturally. This leaves them with immunity and both core and surface antibodies as markers of that immunity following infection.
Children in particular don’t clear the virus and go on to chronic Hep B. With this they typically have core antibodies but no surface antibodies. The surface antibodies are the ones that provide the immunity and don’t develop allowing the chronic infection. People with chronic Hep B usually continue to have measurable levels of surface antigen and DNA on PCR, although some fall below what we can measure.
Typically with chronic infection people are in what’s know as immune control in that their bodies keep the Hep B almost in check grumbling along.
So
1) If you don’t have Hep B antibodies you can not possibly be at risk of reactivation although you are at risk of primary infection
2) If you just have Hep B surface antibodies you are immune due to immunisation and at no risk of reactivation
3) If you have Hep B core and surface antibodies you are immune due to infection and at no or negligible risk of reactivation
4) If you have Hep B core antibodies, but no surface antibodies you have CHRONIC Hep B and are in the risk group. This is regardless of whether you have surface antigen, or PCR DNA because the presence of surface antibody is protective
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