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Old meningitis B vaccine 'may also protect against gonorrhoea'

"Meningitis vaccine may also cut risk of 'untreatable' gonorrhoea, study says," is the headline in The Guardian.

The news comes from the results of a study in New Zealand that found people who'd been given an old version of the meningitis B vaccine were less likely to be diagnosed with gonorrhoea.

But no protective effect was found for chlamydia, which is often diagnosed at the same time as gonorrhoea.

The publication of the study is timely – just last week the World Health Organization issued a warning about the rise in antibiotic-resistant strains of gonorrhoea.

The researchers claim this is the first vaccine to show any protective effect against gonorrhoea, but the vaccine in question is no longer in use.

variant of the vaccine is currently given to babies in the UK as part of the routine NHS vaccination schedule. As the New Scientist magazine speculates, if the biological mechanism is discovered, we may see a sudden drop in gonorrhoea cases in 20 years' time.

But it's unlikely that a dedicated vaccine against gonorrhoea will be available for at least a few years. And that prospect is not a certainty by any means.

For now, the most effective way to prevent gonorrhoea is to always use a condom during sex, including oral and anal sex.

Where did the story come from?

The study was carried out by researchers from Sexual Health Services, Waikato District Health Board, and the University of Auckland in New Zealand, and Cincinnati Children's Hospital in the US.

The research was funded by GSK Vaccines, a pharmaceutical company, and Auckland UniServices, a branch of the university that partners academics with industry. No conflicts of interest were declared.

The study was published in the peer-reviewed journal The Lancet.

The UK media's reporting was generally accurate – but the headlines weren't.

The Guardian's headline talks about "untreatable" gonorrhoea, but the study didn't look at whether any of the people had drug-resistant gonorrhoea or not. The research looked at data captured between 2004 and 2016, when drug-resistant gonorrhoea was less of a concern.

The Independent's headline – "World first as scientists develop vaccine that reduces chance of catching gonorrhoea" – is also inaccurate. The vaccine in question already existed, and it hasn't definitely been proven to reduce the chances of catching gonorrhoea.

What kind of research was this?

This case-control study looked at people with a gonorrhoea diagnosis and whether or not they'd had a meningitis vaccination in the past to see if there was an association. 

Gonorrhoea is a sexually transmitted infection caused by Neisseria gonorrhoeae bacteria, and is associated with multiple issues, including pelvic inflammatory disease, infertility and chronic pain.

Antimicrobial resistance has increased in recent years, and some strains of the infection are now resistant to drugs.

Researchers previously noted a decline in gonorrhoea diagnoses in New Zealand after a mass vaccination programme for meningococcal B, a serious cause of life-threatening infections such as meningitis and blood poisoning.

Meningitis B is caused by Neisseria meningitides, a bacteria similar to the one that causes gonorrhoea, so experts thought the MeNZB vaccine may be able to protect against both.

This type of research is useful for looking at a large population of people and examining trends and associations – but it can only show a link, not prove cause and effect.

randomised controlled trial would be needed to do this, where the vaccine is offered to some people and not others, but this would be unethical.

What did the research involve?

Researchers looked at 14,730 people aged between 15 and 30 who received a positive diagnosis of gonorrhoea or chlamydia at a sexual health clinic between 2004 and 2016.

They wanted to see if having the meningococcal B vaccine decreased the risk of getting gonorrhoea.

Of those involved, 1,241 people had a gonorrhoea-only diagnosis. Chlamydia-only diagnoses were used as the control group, which included 12,487 people.

Coinfection with both gonorrhoea and chlamydia is relatively common in sexually active adults who don't use condoms.

This means someone being diagnosed with chlamydia but not gonorrhoea could be the result of the meningococcal B vaccine.

Further analysis was done to include the 1,002 people who had both infections.

The researchers looked back over records from the New Zealand National Immunisation Register to identify which participants had received the MeNZB vaccine between 2004 and 2006.

They were able to link people diagnosed with gonorrhoea or chlamydia to their vaccine history through unique National Health Index numbers. They then adjusted the results for ethnicity, deprivation levels, geographical area and sex.

What were the basic results?

The researchers found 41% of the participants diagnosed with gonorrhoea only had been vaccinated against meningitis B, compared with 51% of the chlamydia-only group.

They also found:

  • People who had been vaccinated were 31% less likely to have a gonorrhoea diagnosis than a chlamydia diagnosis (adjusted odds ratio [aOR] 0.69, 95% confidence interval [CI] 0.61 to 0.79).
  • The effect of vaccination appeared to decrease over time. Subgroup analyses found the effectiveness of the vaccine was 20% in the period immediately after the vaccination programme from 2004-09 (95% CI 2% to 34%) compared with 9% from 2010-14 (95% CI 0% to 25%).
  • When people with coinfection were included in the gonorrhoea group, the effectiveness of the vaccine reduced to 23% (95% CI 15 to 30).

How did the researchers interpret the results?

The authors concluded that, "Exposure to [the] MeNZB [vaccine] 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." 

Conclusion

This large study found an association between having the MeNZB vaccine and a reduced likelihood of being diagnosed with gonorrhoea.

But it's difficult to form any firm conclusions because of the nature of the case and control groups.

For example, given that both groups were sexually active, we don't know why the majority of people with gonorrhoea didn't also have a chlamydia infection, and how this may have affected the results.

It could just be down to pure chance and have nothing to do with the vaccine.

So before we celebrate the alleged "cure of gonorrhoea", there are many things to consider:

  • The vaccine in question is no longer in use as a vaccine against meningococcal B. The Men4C jab is now used in the UK. Though it does have many similar components, we don't know if these are useful in protecting against gonorrhoea. Research now needs to focus on whether the association still exists with the new jab.
  • Although the authors adjusted for some variables, other factors might be at play that may have affected the results, such as people's education, diet, and immune system strength.
  • No new vaccine has actually been developed. The indication that something in the MeNZB vaccine might increase protection against gonorrhoea requires further research to pinpoint how it does so.
  • The research was only conducted on people who were diagnosed at a sexual health clinic, and didn't include data from GP surgeries. Many cases in the community could have been missed, and these people could have different immunisation trends.
  • We don't know how long the potential protective effect lasts for, as it seemed to decrease over time.

It's very much a case of "if" rather than "when" a gonorrhoea vaccine is developed. For now, the best way to protect yourself against gonorrhoea, chlamydia and other STIs is to always use a condom during vaginal, oral and anal sex.

Read more about how to have safe sex.