Meningitis vaccine shows protection against gonorrhea

Researchers in New Zealand said they found the first evidence that a vaccine was effective in preventing gonorrhea.

The vaccine, MeNZB, was developed to combat an epidemic of meningitis B in New Zealand, where the government offered it for free to anyone under the age of 20 years between 2004 and 2006. However, according to the results of a retrospective study published in The Lancet, it also offered protection against gonorrhea, with a vaccine effectiveness of 31%.

MeNZB is no longer available, but a similar meningococcal B vaccine currently licensed in several countries, including the United States, could offer similar protection against gonorrhea, according to Helen Petousis-Harris, PhD, senior lecturer in the department of general practice and primary health care at the University of Auckland, and colleagues.

The results of their study were published days after WHO warned that gonorrhea — a once easily curable STD — was becoming untreatable. The warning coincided with a study showing that 66% of 71 countries reporting data saw evidence of drug-resistant strains of gonorrhea between 2009 and 2014, although experts believe the number of countries impacted by the problem is much higher.

An estimated 78 million people are diagnosed with gonorrhea each year, including hundreds of thousands of reported cases in the U.S., where highly resistant strains of the STD have been reported. Efforts are under way to develop new treatments for the infection, but a vaccine will ultimately be needed, according to one of the authors of the study at the center of the WHO warning.

According to Petousis-Harris and colleagues, although efforts to develop a gonorrhea vaccine have been unsuccessful for more than a century, past evidence has suggested that the type of drug used in New Zealand — a group B meningococcal outer membrane vesicle (OMV) vaccine — could affect the incidence of the STD. In their study, they said even modest protection from such a vaccine “would have substantial public health benefits in view of the prevalence of gonorrhea.”

“Modelling suggests that a vaccine with 30% efficacy could decrease the prevalence of gonorrhea by more than 30% within 15 years if immunity is maintained. Higher efficacy offering sustained protection results in greater reductions over a shorter period,” they wrote. “This potential benefit is of even greater importance in view of the increase in antibiotic resistance.”

Additional study warranted

According to the New Zealand Ministry of Health (MOH), MeNZB was developed as a short-term measure to stop an epidemic that was discovered by scientists in the late 1990s. Between July 19, 2004, and June 30, 2006, the vaccine was delivered through schools and primary care to patients aged 6 months to 20 years. Infants and preschoolers were routinely immunized through 2008, according to the MOH. In all, more than 1.1 million people received MeNZB before it was discontinued amid significantly decreased rates of infection.

Using data from sexual health clinics, Petousis-Harris and colleagues conducted a retrospective case-control study of patients aged 15 to 30 years who were born in the years 1984 through 1998, were diagnosed with gonorrhea or chlamydia or both, and who were eligible to receive MeNZB. The 11 sexual health clinics that agreed to participate are from six diverse geographical regions covering 64% of the population of New Zealand, according to Petousis-Harris and colleagues.

The researchers included clinical cases of Neisseria gonorrhea infection and used positive tests for chlamydia as controls. During the study period, there were 1,241 incidences of gonorrhea, 12,487 incidences of chlamydia and 1,002 incidences of coinfection. According to Petousis-Harris and colleagues, patients who received MeNZB were significantly less likely to have the infection than controls — 41% vs. 51%, with an adjusted OR of 0.69 (95% CI, 0·61 to 0·79).

And although MeNZB is no longer available, Petousis-Harris and colleagues said the OMV antigen it contained is included in a meningococcal B vaccine that has been licensed in several countries.

“Based upon our results, assessment of this vaccine's potential effect on gonorrhea infection seems warranted,” they wrote. “Although an efficacy trial would be the gold standard, a before and after study in a population would be low cost and practical. Human challenge studies are also feasible, and could provide valuable additional information.”

Future vaccine development

In a related editorial, Kate L. Seib, PhD, research leader in the institute for glycomics at Griffith University in Southport, Australia, identified the newer OMV meningococcal B vaccine as Bexsero (GlaxoSmithKline), which has been approved in the U.S. for patients aged 10 to 25 years.

Seib said further evidence is needed to support the hypothesis that it offers cross-protection against gonorrhea, but that reduced rates seen in New Zealand after vaccination with MeNZB “support the feasibility of a vaccine to protect against gonorrhea.”

“Further investigation of the antigens and mechanisms responsible for the MeNZB–mediated protection against gonococcal infection will provide unique information to guide future vaccine development,” she wrote. “In light of the high burden of disease and the threat of gonorrhea becoming untreatable because of antibiotic resistance, there is an increased imperative to revisit vaccine options and reinvigorate research in this field.” – by Gerard Gallagher

References:

Petousis-Harris H, et al. Lancet. 2017;doi:10.1016/S0140-6736(17)31449-6.

Seib KL. Lancet. 2017;doi:10.1016/S0140-6736(17)31605-7.

Disclosure: Please see the full study for a list of all authors’ relevant financial disclosures. Seib reports being supported by a career development fellowship from the Australian National Health and Medical Research Council.