Gonorrhea, caused by the bacterium Neisseria gonorrhoeae, is a common sexually transmitted infection. Every year, about 400,000 Americans are infected with gonorrhea; worldwide, the incidence is 78 million. Consequences of gonorrhea include pelvic inflammatory disease, infertility and chronic pain.
For these reasons, researchers have tried to make a vaccine to prevent gonorrhea. Strategies have included a whole cell vaccine, a partially disrupted bacterial vaccine, and subunit vaccines containing either a single pilus protein or PorA (porin) protein. None of the strategies were effective, which is why a recent publication in The Lancet was so surprising.
On July 10, 2017, Helan Petousis-Harris and coworkers at the University of Auckland in New Zealand, in collaboration with researchers at Cincinnati Children’s Hospital, published a study showing some success in protection against gonorrhea (Petousis-Harris H, Paynter J, Morgan J, et al. Effectiveness of a Group B Outer Membrane Vesicle Meningococcal Vaccine Against Gonorrhea in New Zealand: A Retrospective Case-Control Study. Lancet. 2017 Jul 7. pii: S0140-6736(17)31449-6. doi: 10.1016/S0140-6736(17)31449-6.).
Between 2004 and 2008, a vaccine containing the outer membrane vesicle of a meningococcal serogroup B strain was introduced into Australia and given as a three-dose vaccine to children up to 20 years of age. About 1 million children received this vaccine (called MeNZB™). The authors found that MeNZB protected not only against N. meningitides (about 70 percent efficacy), it also protected against N. gonorrhoeae. Vaccine effectiveness of MeNZB against gonorrhea, after adjusting for ethnicity, gender and geographical area was 31 percent (p<0.0001).
While this might seem like an unusual outcome, N. meningitides and N. gonorrhoeae share similar proteins on their outer membrane. A commercial preparation of MeNZB is not available in the United States. However, Bexsero®, which contains the MeNZB outer membrane vesicle in addition to three other proteins, is available. It would be interesting to determine whether those immunized with Bexsero in the United States shared a similar level of protection against gonorrhea as was found in Australia.