KATHERINE ATKINSON

A vaccine for gonorrhoea, which is a sexually transmitted infection (STI), may be accessible in the near-future. Vaccines are responsible for prevention and sometimes even eradication of infectious diseases. On 10 July, an academic journal, The Lancet, released a paper which indicates that a vaccine for gonorrhoea may be a future possibility.

Professor Remco Peters, a medical microbiologist at the University of Pretoria, a clinical programme specialist at Anova Health Institute and an expert in the field of STIs, explains th at vaccines work by “giving [someone] a little bit of the bacteria or virus that you are trying to protect [against]”. This bacteria or virus can either be “a small attenuated piece” or “a synthetically derived component”. This helps the body build an immune response as the disease becomes recognisable.

Gonorrhoea is caused by the bacteria Neisseria gonorrhoeae and can be spread by unprotected vaginal, oral and anal sex, says the NHS website. Gonorrhoea is also known as “the clap”. Symptoms may include thick yellow or green discharge from the vagina or penis, pain when urinating, and bleeding between periods, however, almost 50% of women and 10% of men experience no symptoms. If left untreated gonorrhoea can cause major complications such as infertility and possible miscarriages among pregnant women.

Usually gonorrhoea is treated with antibiotics, however on 7 July the World Health Organisation (WHO) released a statement saying that antibiotic resistance is making gonorrhoea “much harder, and sometimes impossible, to treat”, which is a concern as each year 78 million people are infected. Prof. Peters says there are several reasons that bacteria such as gonorrhoea become drug resistant. “[A characteristic] of Neisseria gonorrhoea is that it mutates relatively easily”, especially on antibiotic pressure which allows for resistance to develop. Prof. Peters uses the example of ciprofloxacin, an antibiotic that used to be administrated to treat gonorrhoea but no longer works. Gonorrhoea can also easily exchange “genetic material that codes for resistance” with other bacteria, especially of the Neisseria species. Finally, Prof Peters explains that “if you treat gonorrhoea and you don’t get adequate drug levels it [gonorrhoea] is also more likely to become resistant”. Certain tissues allow for less drug penetration and therefore higher resistance, explains Prof Peters. This is the case for extra-genital gonorrhoea infections such as in the pharynx or rectum. WHO has stated that extended-spectrum cephalosporins (ESCs), oral Cefixime or injectable Ceftriaxone (sold under the trade name Rocephin) is the “only single antibiotic that remains effective for treating gonorrhoea”. However, resistance to Cefixime has been reported in over 50 countries.

On 10 July, academic journal The Lancet released a paper entitled “Effectiveness of a group B outer membrane vesicle meningococcal vaccine against gonorrhoea in New Zealand”. The paper states that a meningococcal B (MeNZB) vaccine is associated with reduced rates of gonorrhoea and that this is “the first time a vaccine has shown any protection against gonorrhoea”. The study was conducted in New Zealand and the sample included 15 000 people between the ages of 15-30 who were given the MeNZB vaccine between 2006 and 2008. Prof Peters explains that the MeNZB vaccine offers “cross protection” because the “different Neisseria species [Neisseria meningitidis and Neisseria gonorrhoeae] are genetically closely related”. Since the outside of both bacterium are similar, the “vaccine that is meant for different bacteria actually shows partial or some degree of protection for the other”. Dr Petousis-Harris, co-author of the paper and vaccinologist at the University of Auckland, said in a podcast with The Lancet that individuals who receive the MeNZB vaccine are “significantly less likely to [contract] gonorrhoea”. In fact, the study shows a 10% difference between those who were vaccinated and those who were not. Dr Petousis-Harris says this “might not sound like a lot but once you adjust that and calculate the odds ratio, it converts to a vaccine effectiveness of 31%”. However, Prof. Peters says that a paper has found that for a gonorrhoea vaccine to influence an epidemic, the vaccine effectiveness needs to be about 50-60%. This is quite low in relation to the meningococcal B vaccine efficiency, which he estimates to be between “90-95%, if not higher”. Despite this, Prof Peters believes that the study’s findings are of “huge support in the vaccine movement”. He says the vaccine has helped them discover “immunological information” about gonorrhoea for the first time. This is significant because “for some reason […] gonorrhoea doesn’t really generate an immune response”. This means that whether “you have had gonorrhoea before or not doesn’t matter. If you are exposed again you [will] get gonorrhoea again”. This is unlike other infections, such as a throat infection, where immunity is built up. Dr Petousis-Harris said that gonorrhoea is a difficult disease to manage. Not only is gonorrhea common, it is also “associated with complications such as pelvic inflammatory disease, ectopic pregnancy, can result in infertility and it facilitates HIV transmission,” says Dr Petousis-Harris. Furthermore, Dr Petousis-Harris says that it relies on effective, accessible and relatively cheap anti-microbial treatment and now it has developed resistance to pretty much all drugs and is no longer easy to treat. Although Dr Petousis- Harris says that much research still needs to be done in order to understand the mechanism of the disease and vaccine, this is a significant feat for science.

According to the Vaccines for Africa (VACFA) webpage, vaccines are “biological preparations” that teach the body to fight certain diseases. Currently, more than twenty infectious diseases are vaccine preventable. These include cholera, Hepatitis A, B and E, HPV, influenza, measles, mumps, rabies, rubella, tetanus, tuberculosis, yellow fever and more. Vaccines have prevented severe illness and even death for many, an example being the meningitis vaccine in Africa. After many devastating outbreaks of the disease, in 2001 the Meningitis Vaccine Project vaccinated millions of people living in the “African Meningitis Belt” which includes 25 countries. This vaccine resulted in the reduction of the serious disease by 94%.

Image: Centers for Disease Control and Prevention

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