Impact of vaccination and high-risk group awareness on the mpox epidemic in the United States, 2022-2023: a modelling study

Yin-Chien Lin; Tzai-Hung Wen; Wei-Liang Shih; Sten H Vermund; Chi-Tai Fang

doi:10.1016/j.eclinm.2023.102407

Impact of vaccination and high-risk group awareness on the mpox epidemic in the United States, 2022-2023: a modelling study

EClinicalMedicine. 2024 Jan 5:68:102407. doi: 10.1016/j.eclinm.2023.102407. eCollection 2024 Feb.

Authors

Yin-Chien Lin¹, Tzai-Hung Wen^{1

2}, Wei-Liang Shih^{1

3}, Sten H Vermund⁴, Chi-Tai Fang^{1

3

5}

Affiliations

¹ Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan.
² Department of Geography, National Taiwan University, Taiwan.
³ Infectious Diseases Research and Education Center, Ministry of Health and Welfare and National Taiwan University, Taipei, Taiwan.
⁴ Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT, USA.
⁵ Department of Internal Medicine, National Taiwan University Hospital; and School of Medicine, National Taiwan University College of Medicine, Taipei, Taiwan.

Abstract

Background: The unprecedented global outbreak of mpox in 2022 posed a public health challenge. In addition to the mpox vaccine campaign in the United States (US), community organisations and public health agencies initiated educational efforts to promote sexual risk reduction. This modelling study estimated the impact of the two-dose vaccination campaign and sexual behaviour changes coincident with high-risk group awareness on the mpox epidemic in the US.

Methods: We fitted a deterministic, risk-structured SEIARV model to the epidemic curve of reported mpox cases in the US between May 22, 2022 and December 22, 2022. We evaluated the putative effects of the two preventive responses in the US -- vaccination and sexual risk reduction -- at the population-level, by calculating the prevention percentages of cumulative cases compared to the counterfactual scenario without interventions. We performed sensitivity analyses with four parameters: case reporting fidelity, vaccine effectiveness, proportion of asymptomatic cases, and assortative mixing.

Findings: Model fitting revealed a basic reproduction number of 3.88 and 0.39 for the high-risk and low-risk populations, respectively, with 71.8% of mpox cases estimated from the high-risk population. A two-dose vaccination campaign, solely, could prevent 21.2% (10.2%-24.1%) of cases, while behaviour changes due to high-risk group awareness alone could prevent 15.4% (14.3%-20.6%). The combination of both measures were synergistic, with the model suggesting that 64.0% (43.8%-69.0%) of US cases were averted that would have otherwise occurred.

Interpretation: Our models suggest that the 2022-2023 mpox epidemic in the US was controlled by a combination of two-dose mpox vaccination campaign and high-risk group awareness and sexual risk reduction.

Funding: Taiwan Ministry of Education grant #NTU-112L9004, Taiwan National Science and Technology Council grant #MOST-109-2314-B-002-147-MY3 and grant #NSC-112-2314-B-002-216-MY3. SHV was supported, in part, by US National Institutes of Health grant #P30MH062294.

Keywords: Awareness; Mathematical modelling; Mpox; Sexual behaviour changes; US outbreak; Vaccination.

Abstract

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