A vaccine has, for the first time, shown protection against contracting the sexually transmitted infection gonorrhoea, according to researchers.
They noted that some strains of gonorrhoea were now resistant to all available drugs, making vaccine development an urgent global health priority.
“This is the first time a vaccine has shown any protection against gonorrhoea”
They found that exposure to the meningococcal group B vaccine during a mass immunisation campaign in New Zealand was also associated with a reduced likelihood of contracting gonorrhoea.
It is the first time that a vaccine has shown any protection against gonorrhoea, and may provide a new avenue for vaccine development, according to the researchers.
If the effect is confirmed in other studies, administering the vaccine in adolescence could result in significant declines in gonorrhoea, suggested the researchers in The Lancet.
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 now 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 one million individuals – 81% of the population under 20 years – received the MeNZB vaccine during a mass immunisation programme in 2004-06.
The 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 2004-06 vaccination programme.
“Administering it in adolescent immunisation programmes could result in declines in gonorrhoea”
A total of 14,730 cases and controls were included in the analysis – 1,241 cases of gonorrhoea, 12,487 cases of chlamydia, 1,002 cases of co-infection.
Vaccinated individuals were significantly less likely to have gonorrhoea than controls – 41% versus 51%.
Taking into account all other factors such as ethnicity and geographical area, the researchers concluded that having previously received the MeNZB vaccine reduced the incidence of gonorrhoea by approximately 31%.
Lead study author Dr Helen Petousis-Harris, from the University of Auckland, said: “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,” she added.
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 said that more research was now needed to see whether other meningococcal vaccines have a similar effect, and to understand the immunological mechanism.
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.
Study co-author Professor Steven Black, from Cincinnati Children’s Hospital in the US, added: “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,” he said.
The UK have recently introduced the 4CMenB vaccine for infants and it has also been used in the US, Canada, and Australia.