First vaccine to show protection against gonorrhoea suggests new avenue for vaccine development

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Adapted
Media Release
Some strains
of gonorrhoea are now resistant to all available drugs, making vaccine
development an urgent global health priority.
Exposure to
the meningococcal group B vaccine during a New Zealand mass vaccination
campaign was associated with a reduced likelihood of contracting gonorrhoea,
compared with unvaccinated people, according to a new study of more than 14000
people published in The Lancet. This is the first time that a vaccine has shown
any protection against gonorrhoea, and may provide a new avenue for vaccine
development.
If the
effect is confirmed in other currently available and similar meningococcal
group B vaccines, administering the vaccine in adolescence could result in
significant declines in gonorrhoea, which has increasingly become drug
resistant.
The
importance of a vaccine candidate that may have even a moderate effect on
reducing rates of infection is highlighted in a new report by The Lancet
Infectious Diseases journal published which urges global policy action to
address sexually transmitted infections (STIs).
So far,
efforts to develop a vaccine against gonorrhoea have been unsuccessful despite
more than a century of research. Four vaccine candidates have reached clinical
trial stage but none have been effective. However, population data suggests
there is a decline in gonorrhoea immediately after the use of the outer
membrane vesicle (OMV) meningococcal group B vaccine in Cuba, New Zealand, and
Norway.
Despite the
two diseases being very different in terms of symptoms and mode of
transmission, there is an 80-90% genetic match between the Neisseria
gonorrhoeae and Neisseria meningitidis bacteria, providing a biologically
plausible mechanism for cross-protection.
In New
Zealand, approximately 1 million individuals (81% of the population under 20
years) received the MeNZB vaccine, an OMV meningococcal group B vaccine, during
a mass immunisation programme in 2004-2006, providing a unique opportunity to
test the cross-protection hypothesis.
In this
study, researchers used data for all people aged 15-30 who had been diagnosed
with gonorrhoea or chlamydia, or both, at 11 sexual health clinics and who were
eligible to receive the MeNZB vaccine during the 2004-2006 vaccination
programme. Cases had laboratory confirmed gonorrhoea, and controls had
laboratory confirmed chlamydia.
A total of
14730 cases and controls were included in the analysis (1241 cases of gonorrhoea;
12487 cases of chlamydia; 1002 cases of co-infection). Vaccinated individuals
were significantly less likely to have gonorrhoea than controls (41% vs 51%).
Taking into account all other factors such as ethnicity, deprivation,
geographical area, and gender, the researchers conclude that having previously
received the MeNZB vaccine reduced the incidence of gonorrhoea by approximately
31%.
Dr Helen
Petousis-Harris, University of Auckland, New Zealand, and lead author of the
study says: “Our findings provide experimental evidence and a proof of
principle that an OMV meningococcal group B vaccine could offer moderate
cross-protection against gonorrhoea. This is the first time a vaccine has shown
any protection against gonorrhoea. At the moment, the mechanism behind this
immune response is unknown, but our findings could inform future vaccine
development for both the meningococcal and gonorrhoea vaccines.”1
MeNZB was
developed to control a meningitis epidemic and is no longer available, but the
OMV antigens thought to provoke the immune response to gonorrhoea have been
included in the more recently developed 4CMenB vaccine, available in many
countries. The authors say that more research is now needed to see whether
other meningococcal vaccines have a similar effect, and to understand the
immunological mechanism.
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Previous
models have suggested that a vaccine with 30% efficacy could decrease
prevalence of gonorrhoea by more than 30% within 15 years, if immunity is
maintained. Higher efficacy would offer greater protection over a shorter
period of time.
Co-author of
the study, Professor Steven Black, Cincinnati Children’s Hospital, USA, adds:
“The potential ability of an OMV group B meningococcal vaccine to provide
even moderate protection against gonorrhoea would have substantial public
health benefits in view of the prevalence of gonorrhoea, and the increase in
antibiotic resistance. If the 4CMenB vaccine, which is currently available in
many countries, is shown to have a similar effect to the MeNZB vaccine, then
administering it in adolescent immunisation programmes could result in declines
in gonorrhoea.” 1
The authors
note that because of the variability of different strains of N. gonorrhoeae and
N. meningitidis bacteria, the effect of the vaccine might vary depending on the
strain. And being co-infected with chlamydia slightly reduced the effectiveness
of the vaccine.
In the USA,
all teens and pre-teens as well as some children and adults are advised to get
one of two meningococcal vaccines. The UK have recently introduced the 4CMenB
vaccine for infants and it has also been used in the USA, Canada, and
Australia.2
There are
approximately 78 million new cases of gonorrhoea worldwide each year. An
increasing number of strains of the bacteria N. gonorrhoeae have developed
antimicrobial resistance to all drugs recommended for treatment. Untreated,
gonorrhoea can lead to complications of infection, such as pelvic inflammatory
disease, ectopic pregnancy, and infertility, and the infection can facilitate
the transmission of HIV.
The study is
published alongside a Commission in The Lancet Infectious Diseases, launched at
the STI & HIV World Congress in Rio de Janeiro, Brazil on Sunday 9th July.
The report tackles five key areas for STI control, including challenges in
controlling or treating chlamydia, gonorrhoea, and bacterial vaginosis,
diagnosis and control of STIs in low-income and middle-income countries, and
how medical interventions to curb HIV infection might affect other STIs.
Lead author
of The Lancet Infectious Diseases Commission, Professor Christopher Fairley,
Melbourne Sexual Health Centre, Carlton, Australia, says: “STIs remain a
neglected issue globally. Policy makers need to be convinced that investment in
clinical and public health strategies can improve the control of STIs, but
relying only on reducing sexual risk practices at a population level will not
be enough, and research into biomedical treatment will be required. Ultimately,
the development of vaccines against both extensively drug resistant gonorrhoea
as well as chlamydia are likely to be the only sustainable solutions to control
these infections.” 1
The study
(Petousis-Harris et al.) was funded by Novartis Vaccines & Diagnostics and
sponsored by Auckland UniServices.
Article:
Effectiveness of a group B outer membrane vesicle meningococcal vaccine against
gonorrhoea in New Zealand: a retrospective case-control study, Helen
Petousis-Harris, Janine Paynter, Jane Morgan, Peter Saxton, Barbara McArdle,
Felicity Goodyear-Smith, Steven Black, The Lancet Infectious Diseases, doi:
10.1016/S0140-6736(17)31449-6, published online 10 July 2017.
Comment:
Gonorrhoea vaccines: a step in the right direction, The Lancet Infectious
Diseases, doi: 10.1016/S0140-6736(17)31605-7, published online 10 July 2017.
Commission: Sexually
transmitted infections: challenges ahead, Prof Magnus Unemo, PhD et al., The
Lancet Infectious Diseases, doi: 10.1016/S1473-3099(17)30310-9, published 9
July 2017.
SOURCE:
MEDICAL NEWS TODAY
Kayode Ojo
Kayode Emmanuel Ojo is the Co-Founder and Managing Director at SHEFFA Limited. He is presently studying Computer Science at the National Open University, Victoria Island, Lagos.