Recent reports of multi-drug resistant gonorrhea have aroused particular concern because it was thought impossible to create a vaccine against the sexually transmitted infection. Yet we've now learned that not only does such a vaccine exist, but it was made by accident in the process of making one against meningococcus.
Vaccines began as protection against diseases you can't get twice. When exposed to certain bacteria or viruses, the immune system creates a memory that protects against reinfection. Vaccines provide a way to create this memory without needing to get sick.
Unfortunately, some diseases, including gonorrhea, don't produce the same immune reaction. You can get gonorrhea, be treated with antibiotics, and be reinfected. This makes producing a vaccine against the Neisseria gonorrhoeae bacterium immensely challenging, although one has shown promise in mice. Dr Helen Petousis-Harris of the University of Auckland noted in a statement: "Despite efforts, a gonorrhea vaccine with any clinical effect has eluded development for over 100 years.”
Yet Petousis-Harris discovered that such a vaccine exists, albeit imperfectly. It's called the MeNZB vaccine and it helped stop a New Zealand meningitis epidemic from 2004 to 2006.
The epidemic was caused by the Neisseria meningitidis B bacteria, part of the same genus as gonorrhea. Infection can cause an infection of brain membranes (meningitis) or blood poisoning (septicemia). The vaccine had 77 percent effectiveness, enough to produce herd immunity in this case.
Years later, when studying gonorrhea infections, Petousis-Harris discovered that, in a sample of records from 11 health clinics, 41 percent of people who had received the MeNZB vaccine had gonorrhea, but the rate was 51 percent among the unvaccinated. After making allowance for factors such as geography, sex, and economic disadvantage, Petousis-Harris estimated in The Lancet that the vaccine provides 31 percent protection, at least for 10 years after injection.
If you want to protect yourself against gonorrhea, which is a good idea given the extent to which antibiotics are failing, condoms are a much better bet. However, if we can get this level of prevention against gonorrhea without even trying, Petousis-Harris thinks we should be able to produce something better if we actually work for it, using MeNZB as a starting point.
Moreover, many countries are already trying to get teenagers and preteens to get vaccinated against meningococcal bacteria strains. Partial protection against a sexually transmitted infection might just sweeten the deal enough to get some extra people vaccinated.
The MeNZB vaccine is now outdated, but Petousis-Harris thinks the widely available 4CMenB (Bexsero) vaccine probably has similar effects. If so, it could be very helpful. Even a low level of protection can slow the spread of an infectious disease, since protected people don't infect others, potentially buying time to invent new gonorrhea treatments.