For a long time now meningococcal vaccines have been able most of the main serogroups of Neisseria meningitidis pathogenic to humans (A,C, W135, Y using the polysaccheride capsule as the antigen), except one, serogroup B.
There is a good reason why Neisseris meningitidis serogroup B is so difficult to vaccinate against. Its polysaccheride capsule is antigenically very similar to antigens on human cells, therefore it does not trigger an immune response.
To get around this researchers have had to “look harder” for antigenic components on the cell surface of Neisseria meningitidis, and that are found in most serogroup B Neisseria meningitidis bacteria circulating globally.
For Bexsero, these are:
- Factor H Binding Protein (fHbp)
- Neisseria Heparin Binding Antigen (NHBA)
- Neisserial Adhesin A (NadA)
- The antigenic component fron the NZ MeNZ B vaccine. (outer membrane vesicle)
This is not the first Meningococcal vaccine to be introduced. As can be seen above, NZ had a serogroup B meningococcal vaccine available from 2004-2008 to counteract a serogroup B epidemic in the country at that time. However this vaccine was specifically designed to provide immunity against this particular serogroup B strain and would not have provided protection against serogroup B disease on a global scale. Cuba also intoduced a strain specific serogroup B meningococcal vaccine along similar lines.
The new vaccine (Bexsero) is anticipated to “cover” approximately 3/4 of serogroup B disease worldwide. It has performed well in the initial trials but the acid test is now how it will perform in “real life” over a prolonged period of time. It certainly has the potential to further alter the global epidemiology of bacterial meningitis.
This new vaccine may also have implications for microbiology laboratory staff. Microbiology staff are at greater risk than the general population of contracting meningococcal disease, and such a vaccine may be considered (along with other meningococcal vaccines) as a means to reduce this potential occupational risk.
For a nice easy to read Q&A article on the new vaccine, click here
p.s. I have added some MCQs on Neisseria gonorrhoeae to the website.