Meningitis vaccines could help tackle untreatable gonorrhoea

Latest studies from South Australia and the US have indicated that meningitis vaccines could help improve protection against gonorrhoea amid rising cases globally and increasing bacterial resistance to drugs used to treat the infection.

In 2020, more than 80 million new cases of gonorrhoea — a sexually transmitted infection (STI) which, if untreated, can lead to serious health conditions, including infertility in women, transmission to newborn babies — were recorded worldwide.¹

Declining effectiveness of drug treatments for the bacteria responsible — Neisseria gonorrhoeae — and the lack of a licensed vaccine to prevent the infection have raised concerns about the possibility that gonorrhoea may become more resistant to treatment, or even untreatable, in future. In 2016, the WHO set a target to reduce gonorrhoea incidences by 90% by 2030; however, an effective vaccine has yet to be developed.

Meningitis vaccines have been recommended by the WHO as part of its roadmap to reduce the global burden of meningitis. This includes offering these vaccines as part of routine childhood immunisation strategies.² Since meningitis vaccines have become more widely available, studies have shown they also offer some protection against gonorrhoea, and that even partial protection could reduce cases of the infection considerably. However, questions have remained about the impacts and effectiveness of using meningitis vaccines against gonorrhoea.

Three studies, published in The Lancet Infectious Diseases journal, suggest that the 4CMenB vaccine may offer significant protection to young adults, and to men who have sex with men who might be at higher risk of infection.

40% protection

A study led by Dr Winston Abara, of U.S. Centers for Disease Control and Prevention, used health records to identify laboratory-confirmed cases of gonorrhoea and chlamydia — another leading STI — among 16- to 23-year-olds in New York City and Philadelphia from 2016–2018. These cases were compared with immunisation records to determine people’s vaccination status with 4CMenB — which is licensed for use against meningitis — at the time of infection.

There were more than 167,000 infections among almost 110,000 people. A total of 7692 people had received the 4CMenB vaccine, with around 52% people receiving one dose, 47%  two doses and less than 1% more than two doses. Full vaccination, ie two doses, was estimated to provide 40% protection against gonorrhoea. One vaccine dose provided 26% protection.

Dr Winston Abara said the findings suggest that meningitis vaccines that are even only moderately effective at protecting against gonorrhoea could have a major impact on prevention and control of the disease. “Clinical trials focused on the use of 4CMenB against gonorrhoea are needed to better understand its protective effects and could also offer important insights towards the development of a vaccine specifically for gonorrhoea.”

33% protection

South Australia’s ongoing 4CMenB vaccination program is the most extensive globally, initially involving infants, children, adolescents and young adults with a continuing state-funded program for infants and adolescents.

The authors analysed meningitis and gonorrhoea infection data held by the Communicable Disease Control Branch and 4CMenB vaccination records from the Australian Immunisation Register. To estimate the effectiveness of 4CMenB against gonorrhoea, patients diagnosed with chlamydia acted as controls because of similar sexual behavioural risks reported in patients with either infection.

More than 53,000 adolescents and young adults received at least one dose of 4CMenB during the vaccination program’s first two years. As well as being highly effective against meningococcal B meningitis and sepsis, in adolescents and young adults a two-dose course of 4CMenB was 33% effective against gonorrhoea.

Professor Helen Marshall said, “While recent studies have provided evidence that 4CMenB vaccination is associated with reduced risk of gonorrhoea, the vaccine was only offered to adolescents and young adults for short periods. The unprecedented scale of South Australia’s 4CMenB vaccination program offers valuable real-world evidence of the vaccine’s effectiveness against meningococcal B meningitis in children and adolescents, and gonorrhoea in adolescents and young people. This information is vital to inform global meningitis vaccination programs and policy decisions.”

While a meaningful reduction in the rate of gonorrhoea among adolescents and young adults was not observed, this was likely due to small case numbers in this age group. The reported effectiveness of 4CMenB against gonorrhoea is consistent with other studies. Co-infections of gonorrhoea and chlamydia may play an important role in disease spread and severity, but factors associated with rates of co-infections are not well understood. However, the analysis shows effectiveness was similar whether co-infections were included or not.

Health impact and cost-effectiveness

Until now, no study has assessed both the health impact and cost-effectiveness of using a vaccine to avert gonorrhoea infections. A modelling study led by Professor Peter White, Imperial College London, UK, is said to be the first analysis of the health and economic effects of using a vaccine to protect against gonorrhoea that accounts for its impact on future rates of infection.

A simulation model was developed to compare three realistic vaccination approaches among men-who-have-sex-with-men (MSM) in England: vaccination of all men attending sexual health clinics; vaccination following a confirmed gonorrhoea diagnosis; or vaccination based on risk of infection.

Based on their analysis and a balance of cases prevented vs the cost of vaccination, the authors recommend vaccinating MSM at highest risk of gonorrhoea infection with 4CMenB, which would prevent an estimated 110,000 cases and save £8 million over 10 years.

Professor Peter White said, “With a gonorrhoea-specific vaccine likely to take years to develop, a key question for policymakers is whether the meningitis vaccine 4CMenB should be used against gonorrhoea infection. Our analysis suggests that giving the vaccine to those at the greatest risk of infection is the most cost-effective way to avert large numbers of cases.”

The authors explain that their estimation of the benefit of using 4CMenB to protect against gonorrhoea is conservative. Due to a lack of data at the time of the study, it was assumed a first vaccine dose offers no protection so only those who received a second dose were protected; however, the study by Abara and colleagues suggests one dose offers some protection, increasing the benefit of vaccination. Additionally, vaccination will reduce the future impacts of antimicrobial resistance (AMR) — which are likely to be substantial — meaning that vaccination would be even more beneficial than currently estimated, but further studies are needed to assess the potential future burden of AMR.

^{[1] https://www.who.int/publications/i/item/9789240027077
[2] https://www.meningitis.org/meningitis-2030-plan-agreed-by-who}

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