By Kate Kelland
LONDON (Reuters) - 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 findings, published in The Lancet medical journal on Tuesday, mark the first time an immunization has shown any protection against gonorrhea and point to new avenues in the search for a gonorrhea vaccine, scientists said.
"This new research could be game-changing," said Linda Glennie, an expert at the Meningitis Research Foundation who was not directly involved in the study.
Gonorrhea has become an increasingly urgent global health problem in recent years as strains of the bacterial infection have developed high levels of drug resistance.
The World Health Organization warned last week that some totally drug-resistance superbug strains of the disease already pose a major threat.
Yet so far, efforts to develop a gonorrhea vaccine have yielded disappointing results: Four potential shots have reached the clinical trial stage, but none has been effective.
In New Zealand, around 1 million people under age 20 received a meningitis vaccine known as MeNZB during a 2004-2006 immunization program. This provided a valuable opportunity to test for cross-protection, the scientists explained.
For their study, the team used data from 11 sexual health clinics for all people aged 15 to 30 who had been diagnosed with gonorrhea or chlamydia, or both, and who had also been eligible to be immunized against meningitis in the 2004-2006 campaign.
They found that those who had been vaccinated were significantly less likely to have gonorrhea. And taking into account factors such as ethnicity, deprivation, geographical area and gender, having the MeNZB vaccine reduced the incidence of gonorrhea by around 31 percent.
Helen Petousis-Harris, who co-led the study at the University of Auckland, said the findings "provide experimental evidence and a proof of principle" that meningitis vaccines might offer moderate cross-protection against gonorrhea.
"Our findings could inform future vaccine development for both the meningococcal and gonorrhea vaccines," she said.
Despite the diseases being very different in symptoms and transmission modes, she added, the bacteria Neisseria gonorrhoeae and Neisseria meningitidis have an up to 90 percent genetic match, providing a biologically plausible mechanism.
(Reporting by Kate Kelland, editing by Louise Heavens)