A meningitis vaccine could be cost-effective in combating gonorrhoea amid rising cases globally and increased resistance to drug treatments.

This is the finding of a new modelling study published in The Lancet Infectious Diseases journal, which looked at the cost effectiveness of using a vaccine for meningitis B (called ‘Bexsero’) to protect against gonorrhoea.

Gonorrhoea is a sexually transmitted infection (STI) caused by bacteria which, if untreated, can lead to serious health conditions. The World Health Organization has designated gonorrhoea a public health priority, with rising case numbers globally and increases in bacterial resistance to drug treatments raising concerns that gonorrhoea may become untreatable.

There are currently no approved vaccines against gonorrhoea.
Previously, researchers in New Zealand showed that a vaccine used to prevent meningitis offered some protection against gonorrhoea, and it was expected that the similar Bexsero vaccine would be more protective – which has now been confirmed by a separate study.

Measuring cost effectiveness

The question for public health decision makers is, does Bexsero provide sufficient protection to be cost-effective to use against gonorrhoea?

This Imperial modelling study is the first cost effectiveness analysis of any vaccine against gonorrhoea that accounts for the impact of vaccination on future transmission and diagnoses. The researchers considered the costs of vaccination, the cost savings from reduced testing and treatment of gonorrhoea infections, and the value of health gains from averting illness. They found that vaccination could save money overall as well as benefiting health.

In the analysis, researchers considered men who have sex with men (MSM), who are a key affected group internationally, and in England they have the highest incidence of infection – accounting for almost half of diagnosed cases – and the greatest risk of having drug-resistant infection.

If existing meningitis vaccines were targeted towards at-risk groups, they would not only have a large impact on the gonorrhoea epidemic in men who have sex with men, but could also save costs to the NHS Dr Lilith Whittles School of Public Health

The modelling found that it would be cost-effective to use Bexsero to protect MSM against gonorrhoea, provided it were offered to those at higher risk of infection, to maximise the benefit per dose administered.

Offering vaccination to all MSM in England attending sexual health clinics for STI testing was not considered to be a cost-effective approach because it would be expensive and an alternative approach could achieve a similar health benefit whilst actually saving money.

Offering vaccination to those with a confirmed gonorrhoea diagnosis (who are statistically at higher risk of being infected again in the future) would likely be cost-effective, preventing more than 43,900 cases and save more than £2.2 million over 10 years.

Risk-based

Offering vaccination based on future risk of infection (meaning those diagnosed with gonorrhoea plus those reporting high numbers of sexual partners) could prevent even more cases (more than 110,200) and saves even more money (more than £7.9 million) – however, this approach requires asking patients about sexual behaviour, which they might not wish to disclose making it potentially harder to implement.

With efforts underway to produce vaccines specifically to protect against gonorrhoea, an important additional finding is that improving efficacy increases a vaccine’s value more than improving duration of protection.

Professor Peter White, of Imperial College London, said: “We found the most cost-effective approach is offering vaccination to those men who have sex with men (MSM) at highest risk, but this requires asking about sexual behaviour which might be sensitive for some people and so it might be difficult to do in practice, so we recommend sexual health clinics conduct a feasibility study. If we can’t put this approach into practice, then an alternative pragmatic approach is offering vaccination to all MSM testing positive for gonorrhoea, as being diagnosed with gonorrhoea is an indicator of risk of future infection.”

Dr Lilith Whittles of Imperial College London said: “If existing meningitis vaccines were targeted towards at-risk groups, they would not only have a large impact on the gonorrhoea epidemic in men who have sex with men, but could also save costs to the NHS. To inform vaccine developers, we found that although current vaccine-protection is likely to be relatively short-lived, meaning repeated boosters would be needed, improving efficacy increases the value of a vaccine more than improving the duration of protection.”

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‘Public health impact and cost-effectiveness of gonorrhoea vaccination: an integrated transmission-dynamic health-economic modelling analysis’ by Lilith Whittles et al, is published in The Lancet Infectious Diseases.

NOTES: 

Cases increased in England over a decade, peaking at 70,000 in 2019 and remaining very high despite a drop during the COVID-19 pandemic. There were 80 million new cases of gonorrhoea recorded worldwide in 2020.

At the time of the study there was no estimate for the effectiveness of Bexsero against gonorrhoea so to be cautious the study assumed that it was as protective as the earlier MeNZB vaccine (i.e. 31%), even though Bexsero® was expected to be more protective. The study also considered scenarios in which protection was greater, up to 2.5× as protective as MeNZB. Abara and colleagues publish the first estimate of the effectiveness of Bexsero in the same issue of the Lancet Infectious Diseases, reporting it to be 40%, which is within the range considered by the modelling analysis.

Additionally, the duration of protection against gonorrhoea provided by Bexsero is unknown so again the study was cautious and assumed that it lasts for 18 months after primary vaccination and 36 months after a booster vaccine, which is how long Bexsero is estimated to protect infants against meningitis B. Other evidence suggests that protection of adults could last for 4 years, 7.5 years, or even longer, so the modelling also considered these potentially longer durations of protection.

The estimates under the two targeting scenarios of (i) 110,000 cases averted and £7.9 million saved or (ii) 43,900 cases averted and £2·2 million saved over 10 years use the cautious estimates of 31% protection lasting for 18 months after primary vaccination and 36 months after a booster vaccine. Greater effectiveness, as estimated by Abara and colleagues, and/or longer duration of protection would mean more cases averted, and more money saved.