Auckland University researchers have made the surprising discovery that a meningococcal disease vaccine used in New Zealand and Cuba gives about 30 per cent protection against gonorrhoea.

"This is an exciting discovery that has the potential to help combat a very common and distressing disease," said Helen Petousis-Harris, who led the research.

The study findings were presented this week at the International Pathogenic Neisseria Conference in England.

Left untreated, gonorrhoea can cause severe pain and reduced fertility in women.

It has also become resistant to many antibiotics and may soon be untreatable.

In New Zealand, about 3000 cases are reported each year and is the second most reported sexually transmitted bacterial disease, after chlamydia.

The researchers had been looking at figures which showed gonorrhoea cases had dropped following meningococcal vaccine programmes in Cuba and New Zealand, where the MeNZB vaccine was offered between 2004 and 2008.

They used anonymised data from sexual health clinics and the immunisation registry and compared it with chlamydia.

Individuals who received the MeNZB vaccine were 30 per cent less likely to be diagnosed with gonorrhoea.

"This was surprising as the vaccine was very specific for a particular strain of meningococcal disease, it was not designed to protect against gonorrhoea infection," said Dr Petousis-Harris.

The link was plausible because the two bacteria have about 80 to 90 per cent of their primary DNA sequences in common.

The MeNZB vaccine is no longer available but another meningococcal B vaccine, 4CmenB has the same key MeNZB ingredient and may have similar or greater protection against gonorrhoea.

The researchers are looking further into how the vaccine has worked.