Research finds new way to determine protection of Men B vaccine against different strains

In a study funded by Meningitis Research Foundation (MRF), researchers have developed a new approach to assess the effectiveness of the vaccine Bexsero^®, which provides protection against different strains of group B meningococcal meningitis and septicaemia (MenB).

Bexsero^® was introduced into the UK infant immunisation schedule in September 2015 and has been shown to be highly effective in preventing MenB disease in those vaccinated.

People vaccinated against MenB will produce antibodies against a protein called factor H binding protein (fHbp), which can be found on the surface of most MenB bacteria. If a vaccinated person comes into contact with the MenB bacteria that possess this protein, antibodies will bind to and kill the meningococcal bacteria.

In the new study, published in the academic journal PLOS One, researchers at the University of Leicester and Meningococcal Reference Unit show how a combination of DNA sequences and statistical testing can be used to measure the amounts of fHbp present in meningococcal bacteria of patients who had the disease.

Whenever someone becomes ill with MenB it is important to be able to test whether the strain they are infected with might have been prevented by the vaccine. Currently, it is estimated that the vaccine offers protection against 73-88% of strains responsible for meningococcal disease in England and Wales.

The approach is being assessed by Public Health England for its potential to routinely test all meningococcal disease cases.

The research was based on looking at one of the four antigens that make up the vaccine. More work is needed to look at the remaining three antigens. 

Dr Chris Bayliss, from the University of Leicester's Department of Genetics and Genome Biology, said, “This new research fills a gap in current testing capabilities that determine whether a disease-causing meningococcal strain is expected to be covered by the vaccine.

“We are currently unable to obtain and grow live bacteria from up to half of patients to determine whether the vaccine might have prevented the type of meningococcal disease they have, often because treatment with antibiotics has already killed them. There is a need for new tests to identify and measure the amount of antigen by obtaining meningococcal DNA directly from patient blood samples.”

Researchers and Mathematicians at the University of Leicester studied more than 2,000 disease-causing meningococcal isolates to measure how much antigen each strain produces.

They used their results to categorise each strain into three classes: ‘covered’; ‘not covered’; and ‘at risk’. The ‘not covered’ groups included the ~12% of strains that will not be covered by the vaccine while the ‘at risk’ groups contains strains that are more likely to cause illness in vaccinated individuals.

Dr Bayliss said: “Detailed molecular analyses of clinical samples are essential for understanding how efficient the new vaccines against meningococcal disease are at protecting people against different meningococcal strains.

“This novel approach has the potential to help measure the effectiveness of Bexsero^® more accurately. 

“The detailed information collected on the fHbp protein could be important in helping to improve the next generation of MenB vaccines.”

Linda Glennie, Director of Research at MRF said, “Introducing the MenB vaccine into the UK immunisation schedule in 2015 was a major step forward. Vaccines are the only way to prevent bacterial meningitis and septicaemia. The MenB vaccine has already been proven to be safe and effective and rates of MenB have been reducing since the introduction of the vaccine.

“Now that we have a vaccine in the schedule that gives good protection against MenB, these new testing techniques that the scientists have developed will give us crucial insights. Over the years, the strains that circulate in the UK have changed, and it is important to be certain about how much coverage the current MenB vaccines can provide, both now and in the future.”