There is growing evidence to suggest that vaccines licensed to protect against meningitis and septicaemia, caused by meningococcal group B (MenB) infection, can also offer some protection against gonorrhoea.
This could have important implications for future cost effectiveness assessments of teenage MenB vaccination programmes. Below we examine the latest scientific research and what it is telling us about vaccine prevention for both MenB and gonorrhoea.
Real world evidence on the impact and effectiveness of the MenB vaccine Bexsero continues to build
Meningococcal bacteria (Neisseria Meningitides) are one of the leading causes of bacterial meningitis. In the UK, babies and children under-five are at highest risk of disease, but there is a second peak in teenagers and young adults. There are several different groups of meningococcal bacteria that can cause infection but, across Europe, Australia, New Zealand and much of the Americas, most cases are caused by meningococcal group B (MenB).
In 2015, the UK was the first country to introduce a routine MenB programme targeting infants, using the vaccine Bexsero. In 2020, 13 countries had universal MenB vaccination programmes (see our Meningitis Progress Tracker) but it is South Australia that has offered the most comprehensive MenB programme in the world. Their programme targeted 10 age groups, including catch-up programmes for young children (aged 1-3 years), young adults (aged 16-20) and ongoing routine programmes for infants under 1 and adolescents in school year 10 (aged 15 to 16).
MenB vaccines have been shown to be highly successful in protecting vaccinated populations in England from MenB. Now, new findings from South Australia (published in Lancet Infectious Diseases) again support this. These findings show that, two years after the introduction of childhood and adolescent MenB vaccination programmes in South Australia, there was a 60% reduction in incidence of MenB disease in infants aged 12 weeks to 11 months, and a 73% reduction in 15–18 year olds compared to the levels that would be expected with no vaccine in place.
While it’s excellent news that MenB vaccines are now having demonstrable impact, the path to their development and introduction was challenging. This is because, rather than using the sugar coat of the bacteria, MenB vaccines have instead been made using proteins found on the surface of most MenB bacteria.
These proteins aren’t just unique to MenB. They can also be found on the surfaces of other groups of meningococcal bacteria and other types of bacteria which are part of the Neisseria family. This is critical to the vaccines’ ability to offer protection against other types of meningococcal disease such as MenW, and even other infections including the sexually transmitted infection (STI) gonorrhoea (for which no licensed vaccine is currently available). Gonorrhoea is caused by Neisseria gonorrhoea which is part of the Neisseria family (the family MenB also belongs to), with Neisseria meningitides and Neisseria gonorrhoea sharing up to 80-90% of their genomes (or genetic material).
Why is the impact of MenB vaccines on gonorrhoea relevant to meningitis?
The idea that MenB vaccines could offer more far-reaching protection beyond meningitis started to emerge in New Zealand, where a tailor-made outer membrane vesicle (OMV) MenB vaccine, called MenZB, was developed and offered to anyone under the age of 20 during 2004-2006. This was to combat an increasing number of MenB cases linked to one particular strain.
A case control study which followed found that, as well as helping to combat the MenB epidemic, vaccinated individuals who received three doses of the vaccine were 31% less likely than those who were unvaccinated to be diagnosed with gonorrhoea. Similar potential effects have also since been seen in Canada and the United States.
Now, real world evidence continues to grow: the new findings from South Australia mentioned above have revealed that, as well as being highly effective in preventing MenB disease in vaccinated infants and adolescents, the MenB vaccine Bexsero also provides moderate cross-protection against gonorrhoea. Receiving two doses of Bexsero, which includes an OMV component, is estimated to reduce the chances of getting gonorrhoea by 33%.
Similarly, another study recently undertaken in New York and Philadelphia, which assessed the vaccine effectiveness of Bexsero against gonorrhoea in 16-23 year olds, estimated that in those fully vaccinated it was 40% effective at reducing gonorrhoea. For those partially vaccinated it was 26% effective.
The potential for Bexsero to offer protection against gonorrhoea was again confirmed in a new study from Southern California. This found a lower incidence of gonorrhoea in teenagers and young adults who had received at least one dose of Bexsero, compared to those who had received a dose of MenACWY vaccine. This comparison was important because, while Bexsero contains the OMV component also found in gonorrhoea-causing bacteria, MenACWY vaccines (like most other meningitis vaccines) are made by linking the unique sugar capsule of meningococcal bacteria to a protein. This is why MenACWY vaccines can only offer protection against MenA, MenC, MenW and MenY disease. The analyses from this study revealed that gonorrhoea rates were 46% lower among recipients of Bexsero vs. the MenACWY vaccine, which led the authors to conclude, that OMV-based meningococcal vaccines may be a potential tool for gonorrhoea control.
Why is this important?
In the UK, despite teenagers and young adults being the second age group most likely to be affected by MenB, cost effectiveness studies have concluded that the incidence in this age group is still too low to justify immunising teenagers free of charge on the NHS.
The potential for Bexsero to offer protection against gonorrhoea, as well as meningitis, has important implications for measuring the cost-effectiveness of future MenB vaccination programmes in the UK. This is because of the wider health benefits associated with administering this vaccine (i.e. that this could limit the spread of two infections – MenB and gonorrhoea), and the associated cost savings to the NHS.
Even with a relatively modest vaccine effectiveness against gonorrhoea, the potential implications are substantial given that in 2020 the World Health Organization (WHO) estimated there were 82 million new cases of gonorrhoea.
In the UK, it’s the second most common sexually transmitted infection (STI), with cases having increased for the last decade, reaching their highest ever numbers in 2019. New prevention strategies are urgently needed, as gonorrhoea’s resistance to antibiotics continues to grow rapidly and because even people who are successfully treated can still be re-infected in the future.
It is therefore promising for both wider meningitis protection and protection against gonorrhoea that a new modelling study which explored the effectiveness of different vaccination strategies in protecting men who have sex with men (MSM) against gonorrhoea has found that immunising higher risk MSM (defined as being diagnosed with gonorrhoea or having more than five sexual partners a year) could be hugely cost saving to the NHS (saving £7.9 million over 10 years), if the vaccine was offered at the same price per dose as the UK infant programme. This study was conducted before the new findings from South Australia and the US, but was based on similar conservative assumptions that the vaccine would be effective at reducing 31% of gonorrhoea cases.
What does this mean for the future?
These recent finding, not only support the continuation of the MenB vaccination programme in South Australia to protect infants and adolescents against two diseases with one vaccine, but provide essential data to support the wider use of Bexsero elsewhere.
We’ll continue to closely monitor emerging evidence, its implications for the UK given the increased MenB cases in teenagers and young adults reported earlier this year, and for meningitis protection globally.
More on MenB vaccination, including availability in the UK
More on meningitis signs and symptoms