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Revision as of 00:07, 1 July 2005
MeNZB is a vaccine against a specific strain of group B meningococcus, currently being used to control an epidemic of meningitis in New Zealand.
Immunisation with MeNZB requires three doses, administered approximately six weeks apart.
Each dose is 0.5 ml and contains:
- 25 mcg of outer membrane vesicles from the Neisseria meningitidis group B strain NZ98/245
- 1.65 mg of aluminium hydroxide (an adjuvant)
- histidine (to stabilise the pH)
- normal saline
The vaccine does not contain any whole bacteria (alive or dead). The "outer membrane vesicles" it contains are a small part of the "skin" of the bacteria that let the immune system recognise and prepare for being infected with the real thing.
MeNZB vaccine does not contain any human, blood, or bovine products, egg products, neomycin or the preservative thiomersal. There are no live meningococcal bacteria in the vaccine and it is not possible to catch the disease or become a carrier of the disease, from the vaccine.
The adjuvant is required to assist the immune system respond to the outer membrane vesicles in the vaccine. The body won't just accept an injection of outer membrane vesicles on their own (much like the postal service won't accept goods unless they are properly parcelled and addressed). The adjuvant is the "packaging" for the outer membrane vesicles.
The histidine pH buffer is ensure the vaccine stays as close as possible to the pH of human body fluids. This is to ensure the immune system does not waste time trying to neutralise the vaccine instead of responding to the outer membrane vesicles.
The saline (sterile salt and water) is also like packaging. It is required so that all of the above can be dissolved into a solution that can be injected. It is the same salinity (saltiness) as normal human body fluid.
The antigen in MeNZB is prepared from B:4:P1.7b,4 (NZ 98/254 ) N. meningitidis strain, grown in a fermentor. The bacteria are grown in a synthetic culture medium containing sugar, essential amino acids and essential elements such as iron and potassium. The fermentation does not use bovine or porcine products. The cellular outer membranes are extracted with the detergent deoxycholate, which kills the bacteria. Outer membrane vesicles are purified out of the culture medium by ultracentrifugation, stabilised by histidine and then adsorbed to aluminium hydroxide Al(OH)3 as an adjuvant. Purification is achieved by ultrafiltration/diafiltration.