The new study describe the first vaccine candidate to ever show some kind of protection against the infection.
Researchers studying a mass vaccination campaign against meningitis have found a surprising side effect - the shots also offered moderate protection against gonorrhea, a sexually transmitted infection that is causing global alarm.
The World Health Organization warned last week that some totally drug-resistance superbug strains of the disease already pose a major threat.
Oral sex and a decline in condom use are reportedly behind the spread of the disease, which can infect the genitals, rectum and throat.
Gonorrhoea, which affects around 78 million people worldwide, is increasingly becoming resistant to antibiotics - to the extent that some gonorrhoea strains can not be treated with any of the available drugs on the market.
The finding suggests that the outer membrane vesicle (OMV) vaccine against meningitis B might provide a guide toward the first vaccine that would prevent Neisseria gonorrhoeae infection, Petousis-Harris and colleagues wrote in the Lancet Infectious Diseases.
"However, we may have meningococcal B vaccines that provide moderate protection". Despite being very different in symptoms and mode of transmission, there is a genetic match of up to 90 per cent between gonorrhoea and meningitis bacteria. Taking into account other factors - including ethnicity, deprivation, geographical area, and gender - the researchers concluded that having previously received the MeNZB vaccine reduced the incidence of gonorrhoea by approximately 31%.
"Gonorrhoea is a very smart bug", said Teodora Wi, a human reproduction specialist at the Geneva-based United Nations health agency.
Doctors are particularly concerned about the emergence of antibiotic-resistant strains of the bacteria.
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.
Observers had noted that gonorrhea incidence appeared to fall after the vaccination campaign, so Petousis-Harris' group made a decision to see if they could quantify the effect using a case control study of patients at sexually transmitted infection (STI) clinics in New Zealand.
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. The researchers had no information about people's exposure to gonorrhea, only whether people were treated for the infection at a clinic.
It was not known exactly how the meningococcal vaccine worked on the sexually transmitted disease.
The researchers found that people who had been vaccinated with the MeNZB vaccine were less likely to have gonorrhea than those who weren't (41 percent versus 51 percent).
A vaccine against meningitis has an unexpected side effect: It appears to target gonorrhea, too.
We don't know how long the potential protective effect lasts for, as it seemed to decrease over time.
The findings should "reinvigorate" gonorrhea vaccine research, commented Kate Seib, PhD, of Griffiths University in Gold Coast, Australia.
Even modest protection against gonorrhea would be of great public health interest, they noted, since antibiotic treatment of the disease is becoming increasingly hard.