The role of vaccination and public awareness in medium-term forecasts of monkeypox incidence in the United Kingdom

Abstract

Monkeypox virus (MPXV) is spreading rapidly through close human-to-human contact primarily amongst communities of men-who-have-sex-with-men (MSM). Behavioural change arising from increased knowledge and health warnings may decelerate the rate of transmission and Vaccinia-based vaccination is likely to be an effective longer-term intervention. Here we investigate the current epidemic within the UK population and simulate control options over a 12 week projection using a stochastic discrete-population transmission model which includes MSM status, rate of formation of new sexual partners, and an underlying random sized metapopulation structure. We find that the virus may have already infected a significant proportion of the MSM group with the highest sexual activity (32.5%; 15.9% - 44.9% prediction IQR); the associated immunity, albeit among groups that form a small but sexually active part of the MSM community in the UK, coupled to behavioural driven decrease in the transmission rate of individuals infected with monkeypox, leads to case incidence flattening and then declining over the projection period (12 weeks). Vaccination is most beneficial when targeted to MSM with highest activity if delivered in the near term to further interrupt transmission amongst those driving the epidemic.

The fading of the mpox outbreak among men who have sex with men: a mathematical modelling study

“…In contrast with other studies projecting smaller outbreaks of less than 400 cases [34] or more severe and longer-lasting outbreaks without preventing measures [5,33,35], we found that the size of the mpox outbreak was large but self-limited and could have died out within a few months even without behavioural changes or vaccination.…”

“…Our study is in agreement with the theory developed via earlier studies, showing that heterogeneity in number of sexual partners and assortative mixing enhance the likelihood of occurrence of an epidemic and the rapid spread of an infection, but saturation due to infection-induced immunity in the group with higher than the average sexual activity can lead to low endemic levels (see [24][25][26][27][28] and references herein). Our findings also agree with previous studies on MPXV transmission showing that a very small group of MSM with high level of sexual activity can be sufficient to cause large outbreaks in very short time [32,33] and a decline in numbers of casual partners could reduce the epidemic size of mpox [5,33].…”

“…Our findings also agree with previous studies on MPXV transmission showing that a very small group of MSM with high level of sexual activity can be sufficient to cause large outbreaks in very short time 21,22 and a decline in numbers of casual partners could reduce the epidemic size of mpox. 4,22 Our results correspond well also with a study that showed how the observed decline in mpox cases could be primarily attributed to infection-induced immunity. 5 The present study extends earlier findings as our results quantify the contribution of infection-induced immunity and the contribution of behavioural changes and reveal how these factors shaped the outbreak.…”

“…The weekly number of cases peaked within 2-3 months in most countries and then declined [2]. Several factors may have contributed to the abrupt decline, including health communication aimed at increasing awareness and behavioural changes in the affected population, increased immunity due to MPXV infection, public health interventions (such as case finding, contact tracing, vaccination), and a decrease in cultural/social events and traveling after the summer of 2022 [3][4][5][6].…”

“…2 Several factors may have contributed to the abrupt decline, including health communication aimed at increasing awareness and behavioural changes in the affected population, increased immunity due to MPXV infection, public health interventions (such as case finding, contact tracing, vaccination), and a decrease in cultural/social events and traveling after the summer of 2022. [3][4][5] In the Netherlands, the first mpox diagnosis was on 20 May 2022. The number of mpox cases increased sharply in June 2022, but started declining in the second week of July 2022.…”