Kenya may give the world the first vaccine to protect against gonorrhoea, which causes about 87 million infections annually.
Scientists at the Kenya Medical Research Institute (Kemri) and the University of Oxford, UK, plan to recruit 50 Kenyans, aged between 18 and 25 years into a six-month gonorrhoea vaccine trial.
The trials, initially planned to start in June this year, are currently in the final approval phase and will be carried out at the Kemri clinic in Mtwapa, Kilifi County.
Once started, participants in the study – ‘Gonococcal Vaccine Study in Key Populations in Kenya,’ registration number NCT04297436, will get two doses of a meningitis vaccine, two months apart.
The meningitis vaccine called Bexsero and licensed in about 35 countries, but not yet in Kenya, has been found to protect against gonorrhoea.
“New evidence suggests that Bexsero which protects against meningitis may also be effective against gonorrhoea,” says Dr Eduard Sanders and Dr Eunice Nduati of Kemri in the study protocol.
Similar but separate studies are going on in the US and Australia, involving 2,200 and 730 gay men respectively. These trials are investigating the effectiveness of Bexsero to protect against gonorrhoea infections.
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“We want to find out whether participants who receive the meningitis vaccine have fewer new cases of gonorrhoea compared to those who do not receive the vaccine,” says Prof Kate Seib who is leading the Australian study.
But the Kenya experiment has a slightly different approach. “This is not an efficacy trial,” says the study protocol.
The researchers say they want to know whether immunising people with Bexsero will elicit antibodies against gonorrhoea.
An antibody is a protein produced by the body when it detects harmful substances such as disease-causing germs to help fight off the threat.
The researchers will then apply this knowledge to design and develop gonorrhoea specific vaccine; which is still some way down the road.
The search for a gonorrhoea vaccine is informed by a stiff increase of infections across the world due to drug-resistant gonorrhoea strains.
In 2017 the World Health Organisation and the US CDC designated the gonorrhoea bacteria as a ‘high priority antibiotic-resistant pathogen’ and a ‘microorganism with an urgent threat level.’
Since 1936, gonorrhoea has developed resistance to about a dozen types of antibiotics with recent reports indicating resistance to the last line of defense – a combined high dosage of the antibiotics ceftriaxone and azithromycin.
“Gonorrhoea is hard to treat as we have witnessed a lot of drug resistance,” says Rosemary Muraya, the nurse in charge at Nairobi’s Special Treatment Centre otherwise known as Casino or Hospitali ya Kaswende.
The Ministry of Health in its National Guidelines for Prevention, Management, and Control of Sexually Transmitted Infections 2018, blames the gonorrhoea spike on Kenyan’s peculiar sexual habits.
“For example, oral or throat gonorrhoea has become more frequent as a result of engaging in oral sex,” says the guidelines. The ministry blames this habit especially for the emergence of hard to treat gonorrhoea.
Such patients, the guidelines say present with a history of sore throat, loss of voice, and a history of recent unprotected oral sex.
While prevalence is estimated at just about one per cent in the general Kenya population, among men who have sex with men (MSM), rectal gonorrhoea is estimated at 10 per cent.
A recent study among 400 adolescent girls found rates of up to 1.3 per cent, slightly higher than the national average.
The high prevalence of gonorrhoea among male and female sex workers, experts say, make them an obvious target for a vaccine.
But an earlier World Health Organisation (WHO) expert panel on vaccines said such an approach may present some problems.
The number of sex workers and gays, the panel said, is too small to provide a profitable market for private pharma. On the other hand, promoting it as an STI vaccine for sex workers may impede general acceptability.
“The global market for groups such as gays is likely to be relatively small, which will be a consideration for vaccine developers,” says a report of the 2018 WHO panelists.
To increase the number of possible gonorrhoea vaccine targets the meeting suggested widening the net to capture adolescents aged 9-10. This is the same group that is targeted in the ongoing cervical cancer vaccination.
Vaccine for women or the men?
The meeting, in which Kemri participated, also raised issues on whether the vaccine once developed should be given to both males and females.
“The most direct serious disease outcomes of gonorrhoea infection; such as infertility or adverse pregnancy outcomes are among women. In that case, a single-sex vaccination can provide benefits for both sexes through herd immunity,” suggested the panel.
The experts argued that if high coverage is achieved among females, more than 80 per cent, vaccinating males may have no incremental benefits.
In any case, Kenya, which is already vaccinating girls for cervical cancer, can easily add the new vaccine onto the existing pipeline without necessarily bringing in the boys.
The experts also felt that promoting a gonorrhoea vaccine may meet some resistance and suggest it be driven as fertility or healthy pregnancy vaccine, which may be more acceptable.
But promoting it as a sex workers or gay people vaccine, the experts said, would keep away most of the would-be beneficiaries.
The Mtwapa study will take six months, with participants making six visits to the clinic where they will be screened, vaccinated, and blood and other body samples collected.
Eligible participants will be males and females of either HIV statuses. However, they must be healthy, not pregnant, have no bleeding disorders or allergy to vaccines, and willing to donate blood samples for assessment.