The Meningitis B vaccine does not prevent gonorrhoea infections despite being offered to at-risk men, scientists say.
The NHS started offering the vaccine to men who have sex with men last year, after previous studies suggested it might protect them.
But a new trial in Australia, published in the New England Journal of Medicine, has found no significant difference in gonorrhoea infections between men who were given the vaccine and those who were not.
The UK Health Security Agency said its own studies would provide “more robust data” and is not recommending any immediate changes.
Gonorrhoea is a common, bacterial infection which is transmitted through sexual contact.
It can cause pain, unusual discharge and inflammation of the genitals, but in some cases there are no symptoms.
The vaccine, officially known as the 4CMenB vaccine, was designed for preventing meningitis B in babies, but the bacteria that causes the two diseases are closely related.
Since August 2025, gay and bisexual men who have sex with men have been offered the MenB vaccine in the UK, after a number of studies reported a reduction of 38% in gonorrhoea infections for those vaccinated.
However, a new study by Griffith University and the Kirby Institute at the University of New South Wales in Sydney, found evidence to suggest the MenB vaccine is ineffective against gonorrhoea.
The trial – called GoGoVax – monitored 587 men over two years.
Half of the participants were given the MenB vaccine while the other half were given a placebo.
The results showed similar levels of new gonorrhoea infections in both groups – 291 for those who had the actual vaccine and 285 for those who did not.
The report’s authors said their findings were consistent with two other studies and, when taken together, provided “strong evidence that the MenB vaccine is not effective for gonorrhea prevention”.