The Robinson Institute’s Vaccinology and Immunology Research Trials Unit has contributed to several important studies investigating the safety and efficacy of vaccines against the most common and virulent cause of meningococcal disease, Strain B Meningococcal bacteria.
Neisseria meningitides, or Meningococcus bacteria, is a frequent and normally unnoticed inhabitant of the human nasopharynx. Meningococcal disease occurs when the bacteria enter the bloodstream, proliferate rapidly and lead to infl ammation of peripheral blood vessels and the meningeal lining of the brain, resulting in septicaemia and meningitis. In Australia, 10-15% of children and adolescents who acquire the disease lose their lives. Even if they do survive, there is a 40% chance of long term disability due to limb ischaemia requiring amputation, hearing loss, neurological damage or skin scarring.
Australia does not currently have a licensed vaccine to immunise against Strain B Meningococcus, which causes 80% of all cases of meningococcal disease. Licensed vaccines against the less prevalent Strain C Meningococcus have been very successful in substantially reducing cases due to Strain C disease, but don’t offer cross protection against Strain B.
In 2011, there were 22 cases of meningococcal disease in South Australia: 17 of those cases were caused by Strain B Meningococcus.
During 2012, the Vaccinology and Immunology Research Trials Unit (VIRTU) published five studies addressing safety and efficacy of vaccines targeting Strain B Meningococcus. The work represents a fi rst step in the drive towards a new vaccine being licensed for use in Australia.
Unit Director Associate Professor Helen Marshall explained, “Having a vaccine to prevent Strain B Meningococcal infections would be of enormous value. Our recent studies show we are rapidly progressing towards this point.”
A good Strain B Meningococcal vaccine needs to be well-tolerated in recipients of all ages, offer immune protection against all sequelae following infection, and be effective against the different subtypes of the B strain. It must also generate antibodies that persist and provide long-term protection.
The studies conducted so far by Helen and her colleagues looked at the safety and immunogenicity – the capacity of the vaccine to generate effective immune responses – of a Meningococcal Strain B vaccine in toddlers, children, adolescents and adults. The vaccine was found to be well-tolerated and immunogenic in all age groups, suggesting it may be a good candidate for protection against invasive Strain B Meningococcal disease.
“While these studies are promising, we need to complete the final studies before the vaccine can be reviewed for licensing by the regulatory authorities,” said Helen.
“In addition, the ideal immunisation schedule to provide long term protection against invasive meningococcal disease is yet to be established. Monitoring long term persistence of antibodies post immunisation will inform timing of future booster vaccinations to provide the best protection in at risk age groups and in children with underlying immunosuppressive conditions.”
“We also need to refine immunisation protocols for target age-groups,” added Helen.
“Because most Strain B Meningococcal cases occur in children less than 5 years of age, the ideal time point for a meningococcal B vaccine program would be an infant program commencing at 2 months of age. However a school program would also be valuable given there is a second peak of meningococcal disease in adolescence.” Helen and her colleagues at VIRTU are already conducting additional studies aimed at addressing these issues, and hope to contribute to the evidence base supporting licensing of a vaccine against Strain B Meningococcal in Australia.