Hopes to fight untreatable strains of gonorrhoea have risen after it emerged that a new vaccine against meningitis unexpectedly reduced the risk of people getting the sexually transmitted infection, found a New Zealand study.
Some strains of gonorrhoea are resistant to all available drugs, making vaccine development an urgent global health priority. But according to a study, a vaccine has offered protection against the sexually transmitted disease for the first time.
Gonorrhoea spreads through unprotected vaginal, oral or anal sex and many of those who contract the disease experience no symptoms. If left untreated, the disease can cause infertility and can increase the transmission of HIV infection.
The report says a New Zealand meningitis epidemic in the early 2000s prompted the mass vaccination of a million people and fortuitously set the scene for the current study. The vaccine used, known as ‘MeNZB’, was designed to protect against meningococcal group B infection – the cause of the most deadly form of meningitis.
But intriguingly, over the next few years, the report says the scientists noticed fewer gonorrhoea cases than expected in those who had been vaccinated against meningitis.
Dr Helen Petousis-Harris, a vaccine specialist from the University of Auckland who led the study, was optimistic: “Some types of gonorrhoea are now resistant to every antibiotic we have, and there appeared (to be) little we could do to prevent the steady march of gonorrhoea to ‘superbug’ status. But now there’s hope,” she added.
The research team studied over 14,000 people aged 15-30 who’d been diagnosed with gonorrhoea at sexual health clinics across New Zealand and who had been eligible for the MeNZB vaccine during the emergency vaccination programme. They found vaccinated individuals were over 30% less likely to develop gonorrhoea.
The report says despite meningitis and gonorrhoea being very different illnesses, both are caused by bacteria from the same family and share much of the same genetic code, providing a possible explanation for the cross-protection that the team observed.
More than 78m people worldwide get gonorrhoea each year with most infections in men and women under the age of 25. It is the second most common bacterial sexually transmitted infection in the UK after chlamydia. In England alone, almost 35,000 people were affected in 2014.
But, the report says British Association for Sexual Health and HIV’s president, Dr Elizabeth Carlin, who was not involved in the study, was more sceptical: “These early findings are to be welcomed but it’s important to keep in perspective that the vaccine offered only “moderate” protection …. an individual receiving this vaccine remains susceptible to gonorrhoea but just less so than if unvaccinated.”
The MeNZB vaccine used in the current study is no longer manufactured, but Petousis-Harris has high hopes for a similar meningitis vaccine called ‘4CMenB’, available in many countries.
Petousis-Harris was clear about what needed to happen next. “We need an urgent assessment of current meningitis vaccines to see if they protect against gonorrhoea. It may be possible to eliminate many gonorrhoea infections using a vaccine with only moderate protection. It does not need to be perfect,” she added.
Background: Gonorrhoea is a major global public health problem that is exacerbated by drug resistance. Effective vaccine development has been unsuccessful, but surveillance data suggest that outer membrane vesicle meningococcal group B vaccines affect the incidence of gonorrhoea. We assessed vaccine effectiveness of the outer membrane vesicle meningococcal B vaccine (MeNZB) against gonorrhoea in young adults aged 15–30 years in New Zealand.
Methods: We did a retrospective case-control study of patients at sexual health clinics aged 15–30 years who were born between Jan 1, 1984, and Dec 31, 1998, eligible to receive MeNZB, and diagnosed with gonorrhoea or chlamydia, or both. Demographic data, sexual health clinic data, and National Immunisation Register data were linked via patients’ unique personal identifier. For primary analysis, cases were confirmed by laboratory isolation or detection of Neisseria gonorrhoeae only from a clinical specimen, and controls were individuals with a positive chlamydia test only. We estimated odds ratios (ORs) comparing disease outcomes in vaccinated versus unvaccinated participants via multivariable logistic regression. Vaccine effectiveness was calculated as 100×(1–OR).
Findings: 11 of 24 clinics nationally provided records. There were 14 730 cases and controls for analyses: 1241 incidences of gonorrhoea, 12 487 incidences of chlamydia, and 1002 incidences of co-infection. Vaccinated individuals were significantly less likely to be cases than controls (511 [41%] vs 6424 [51%]; adjusted OR 0·69 [95% CI 0·61–0·79]; p<0·0001). Estimate vaccine effectiveness of MeNZB against gonorrhoea after adjustment for ethnicity, deprivation, geographical area, and sex was 31% (95% CI 21–39).
Interpretation: Exposure to MeNZB was associated with reduced rates of gonorrhoea diagnosis, the first time a vaccine has shown any protection against gonorrhoea. These results provide a proof of principle that can inform prospective vaccine development not only for gonorrhoea but also for meningococcal vaccines.
Helen Petousis-Harris, Janine Paynter, Jane Morgan, Peter Saxton, Barbara McArdle, Felicity Goodyear-Smith, Steven Black