CROI 2024 Abstract eBook

Abstract eBook

Poster Abstracts

Conclusion: The circumstances underlying the unprecedented, international outbreak of Mpox in 2022 remain to be fully elucidated. The reemergence of MPVX in 2023 suggests continued circulation in the human population, which is supported by the virus' continued evolution. Ongoing and robust epidemiological and genomic surveillance is required to determine if MPVX has become endemic in populations outside of West Africa. Continued monitoring of the genetic variation of the virus will allow for development of new antivirals and vaccinations with increased efficacy.

Poster Abstracts

426

Plausibility of Sexual Behavior Changes and Role of Vaccination in Mpox Outbreak Control Among MSM Davide Moschese 1 , Alberto Rizzo 1 , Angelo Roberto Raccagni 2 , Andrea Giacomelli 1 , Riccardo Lolatto 3 , Loriana Morelli 1 , Maria Vittoria Cossu 1 , Maria Francesca Lucente 2 , Valeria Micheli 1 , Davide Mileto 1 , Antonella Castagna 2 , Maria Rita Gismondo 1 , Andrea Gori 1 , Giuliano Rizzardini 1 , Silvia Nozza 2 1 Luigi Sacco University Hospital, Milan, Italy, 2 San Raffaele Vita-Salute University, Milan, Italy, 3 San Raffaele Hospital, Milan, Italy Background: The European mpox exponential increase during the early summer 2022 was believed to be linked to major LGBTQI+ sex-related events. However, it inexplicably faded in the last months of the year: main proposed reasons included behavioural changes in sexual habits and immunization through vaccination campaigns started during summer. We compared the trends of mpox and classical STIs in MSM PLWH and PrEP-users in relation to sex-related events and vaccination campaigns in highly-involved European countries over 2022. Methods: We enrolled consecutive self-identified MSM attending two large sexual health clinics in Milan, Italy, from January to December 2022, who underwent an STIs screening and mpox evaluation. We focused on PLWH and PrEP-users for their strict link to healthcare and regular STIs screening. N. gonorrhoeae , C. trachomatis , M. genitalium and mpox were detected through Nucleic Acids Amplification Tests while a serologic Rapid Plasma Reagin test was used to identify new syphilis cases. Also, we noted the timing for major European LGBTQI+ sex-related events and for the beginning of the mpox vaccination campaign. Results: 1281 STIs were diagnosed from January to December 2022, of whom 654 in PLWH, 627 in PrEP- users. STIs peaked as follows: Chlamydia infection in October (49 cases), followed by January and July (42 and 45 cases), gonorrhoea in June (38), November (37) and January (36), syphilis in August (35 cases), February and March (34 each); mpox in June and July (49 cases) [Figure 1]. Conclusion: We found that classical STIs had a fluctuating, still constant presence throughout the year, while mpox showed a decline even if, in the same period, the mentioned events continued to be held. These findings suggest the unlikeliness of a behavioural change in influencing such a decline, putting in a new light the role of vaccination in the MSM community.

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Mpox Vaccination Uptake Among MSM During the 2022 Epidemic: A Single-Center Retrospective Study Yanis Merad , Matthieu Godinot, Dulce Alfaiate, Agathe Becker, Florence Ader,

Anne Conrad, Laurent Cotte Hospices Civils de Lyon, Lyon, France

Background: During the 2022-2023 Mpox outbreak, 5010 cases were reported in France. Among them, an estimated 85% occurred in men who have sex with men (MSM). Smallpox vaccination was offered to at-risk populations in France, including MSM, starting July 2022. We sought to assess the vaccination uptake rate in MSM and the factors associated with vaccination uptake in different MSM risk-groups: people living with HIV (PWH), people who use pre-exposure HIV prophylaxis (PrEP) and other individuals (NPU, non-PrEP users). Methods: A retrospective observational study was conducted in Lyon, France, enrolling MSM presenting at the sexual health clinics of the University Hospital between July 1st, 2022 and February 28th 2023. Data regarding HIV infection, PrEP use, Mpox infection and Mpox vaccination (first dose received) were collected from electronic medical records. All patients gave informed consent regarding vaccination and the use of their data for analysis. Results: A total of 9256 MSM were enrolled, including 1946 PWH, 2528 PrEP users and 4782 NPU. The median age of each group was respectively 51, 34 and 29 years. The vaccination rate of all participants at the end of follow-up was 49.6%. Compared to NPU, it was significantly higher for PrEP users (72.2%) with a relative risk estimate of 1.62 (95%CI 1.56-1.69), and significantly lower for PWH (32.7%) with a relative risk estimate of 0.73 (95%CI 0.68-0.79). Of note, half of PrEP users were vaccinated by day 66 of the vaccination campaign. In multivariate cumulative risk analysis, HIV infection/PrEP use, age and chemsex were all independently correlated with vaccination uptake. Conclusion: Our study demonstrates Mpox vaccination uptake in MSM during the 2022 outbreak in France was high, especially in PrEP users. This could be explained either by the closer follow-up of this group, or their proactive engagement in STI prevention strategies. In contrast, PWH, although regularly followed-up, were less receptive to the vaccination campaign. It is likely that sexual behavior of PWH, hence exposure risk, are noticeably different. Although vaccination is probably not the only explanation, these successful results mirror the sharp decrease of Mpox cases reported after August 2022 in France.

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