Background
In 2022, a global outbreak of mpox occurred among gay and bisexual men who have sex with men (GBMSM). In England, the outbreak was controlled through reductions in sexual risk behaviour and vaccination of high-risk GBMSM. However, mpox continues to circulate, including an expanding outbreak in Africa, and so there is a risk of future outbreaks in the UK and other noon-endemic countries. We evaluated the most cost-effective vaccination strategy to minimise the risk of future mpox outbreaks among GBMSM in England.
Methods
A mathematical model of mpox transmission among GBMSM was developed to estimate the costs per quality-adjusted-life-year (QALY) gained for different vaccination strategies starting in 2024 (20-year time-horizon; 3.5% discount rate; willingness-to-pay threshold £20,000/QALY). The model was calibrated using English surveillance data from the 2022 outbreak and two community surveys. Reactive vaccination (only during outbreaks) and pre-emptive vaccination (continuous routine) strategies targeting GBMSM at high-risk for mpox were compared to no vaccination. Baseline projections incorporated importation of new mpox cases, and a vaccine effectiveness of 78%/89% for 5/10 years with 1/2 doses at £160/dose. Based on the 2022 outbreak, costs were estimated for case management, vaccination and public health responses (PHR) during futures outbreaks.
Results
All vaccination strategies reduced future outbreaks, gained QALYs and reduced costs compared to no vaccination. Continuous pre-emptive vaccination (daily rate 41 doses) was most cost-effective, saving £38.4 million and gaining 546.3 QALYs over 20-years. Threshold analyses suggested vaccination of GBMSM at high-risk for mpox is cost-effective if the vaccine costs less than £636 per dose. Pre-emptive vaccination remains the optimal strategy across numerous sensitivity analyses, including for importation of more severe and transmissible clades, but the optimal vaccination rate can vary. Reactive vaccination only becomes more cost-effective when public health response costs are not included.
Conclusions
Pre-emptive vaccination of high-risk GBMSM is a crucial cost-saving strategy to prevent future mpox outbreaks. Similar vaccination strategies should be considered for GBMSM in other countries to minimise the risk of future outbreaks.
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