O2.1 - Calculating the value of behavioural science and community engagement in promoting vaccination of MSM: a transmission-dynamic health-economic analysis of 4CMenB (Bexsero) vs gonorrhoea as an example

Background: Uptake of MSM-specific vaccination is typically lower than expected from vaccine-acceptability surveys (less than half, for HPV vaccination in England), reducing benefits of programmes. Research into the reasons why vaccine sentiment in MSM is so poorly-understood is lacking – most likely because its value has not been quantified. We assess the importance of this knowledge gap in a health-economic analysis of potentially using 4CMenB to protect MSM against gonorrhoea.

Methods: We use a transmission-dynamic model calibrated to numbers of gonorrhoea tests and diagnoses, and the proportion of diagnosed cases that is symptomatic, using a Bayesian framework. We estimate the impact of offering 4CMenB to higher-risk MSM in sexual health clinics in England, assuming the same uptake as observed for HPV vaccination (i.e. 40.8%(95%CrI:40.6-41.0) of offers are accepted). Typically modelling would assume 40.8%(40.6-41.0) of individuals would accept vaccination each time they are offered. An alternative interpretation is 40.8%(40.6-41.0) are willing to be vaccinated and 59.2%(59.0-59.4) are not. We compare these two interpretations, which bracket the range of possibilities.

Results: In both scenarios the numbers of vaccinations declines over time as numbers of unvaccinated individuals decline. However, in the first scenario the proportion of unvaccinated who accept vaccination stays constant over time, whereas in the second scenario this proportion declines over time, so coverage is lower. If vaccination costs the estimated UK price of £18/dose administered then in the first scenario vaccination saves £12.0M(95%CrI:1.9-24.6) and gains 133.1(46.7-261.9) QALYs over 10 years (with discounting at 3.5%p.a.) whereas in the second scenario it saves only £7.6M(95%CrI:1.2-17.5) and gains only 81.4(28.7-164.2) QALYs.

Conclusion: There will be a spectrum of vaccine sentiment in the population, with reality lying between the two scenarios. The impact of vaccination is ~60% greater in the optimistic scenario (which modelling usually assumes) than in the pessimistic scenario, equivalent to £4.4M and 51.7 QALYs over 10 years for gonorrhoea vaccination alone. Modelling may overestimate the impact of vaccination by many £millions, so it is vital to invest in (i) studying vaccine sentiment in MSM to better-assess the likely impact of programmes, and (ii) community engagement to improve uptake to maximise health-gains and cost-savings.