VHPB consensus statement on HBV mutants and variants. (January 1999)
Source : Fact sheet 4 (see publications)
The present vaccines and vaccination strategies are 90% to 95% effective in reduction of HBV carrier prevalence in immunised cohorts of children, and are highly effective in preventing transmission in other at risk groups. These prevention strategies should be vigorously continued in the over 90 countries that have already introduced universal immunisation, and should be implemented in all countries where not yet in place.
A much more complete understanding of the potential impact of "escape" mutants on the epidemiology and prevention of hepatitis B is needed. In order to reach this goal the following activities should be encouraged and implemented:
- The tools to detect HBV mutants and variants should be optimised:
- there is a need for the evaluation of existing HBsAg diagnostic assays to determine if they detect relevant HBsAg variants and mutants. This will require the development of a serum panel containing such mutated viruses/antigens, and validation by external quality control.
- a true neutralisation assay is necessary to evaluate the potential of mutants to escape passive or active immunisation or natural immunity.
- methods to detect and classify mutants and variants should be standardised. A definition of what is a wild type virus is needed.
- There is a need for a surveillance network to detect HB mutants world-wide.
- Epidemiologic studies are needed to determine:
- the attributable risk of HBV infection from these mutants following post- exposure immunisation.
- the risk of person to person transmission of these mutants in susceptible and immunised humans.
- Research should be encouraged to better understand the mechanisms/ pressures for naturally occurring variants and for mutants induced by passive or active immunisation. For this reason there is need either to further characterise and standardise hepatitis B immunoglobulin preparations or to replace these with pools of monoclonal antibodies with defined properties known to neutralise 'S' mutants, and to further study vaccines which might prevent the occurrence of relevant immune escape mutants.
