Seroprevalence and risk factors of exposure to COVID-19 in homeless people in Paris, France: a cross-sectional study.

BACKGROUND: During the COVID-19 lockdown period from March 17 to May 11, 2020, French authorities in Paris and its suburbs relocated people experiencing recurrent homelessness to emergency shelters, hotels, and large venues. A serological survey was done at some of these locations to assess the COVID-19 exposure prevalence in this group. METHODS: We did a cross-sectional seroprevalence study at food distribution sites, emergency shelters, and workers' residences that were provided medical services by Médecins Sans Frontières in Paris and Seine-Saint-Denis in the Ile-de-France region. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody seropositivity was detected by Luciferase-Linked Immunosorbent Assay and Pseudo Neutralization Test. Sociodemographic and exposure related information was collected via a verbal questionnaire to analyse risk factors and associations with various COVID-19 symptoms. FINDINGS: Between June 23 and July 2, 2020, 426 (52%) of 818 individuals recruited tested positive in 14 sites. Seroprevalence varied significantly by type of recruitment site (χ2 p<0·0001), being highest among those living in workers' residences (88·7%, 95% CI 81·8-93·2), followed by emergency shelters (50·5%, 46·3-54·7), and food distribution sites (27·8%, 20·8-35·7). More than two thirds of COVID-19 seropositive individuals (68%, 95% CI 64·2-72·2; 291 of 426) did not report any symptoms during the recall period. COVID-19 seropositivity was strongly associated with overcrowding (medium density: adjusted odds ratio [aOR] 2·7, 95% CI 1·5-5·1, p=0·0020; high density: aOR 3·4, 1·7-6·9, p<0·0001). INTERPRETATION: These results show high exposure to SARS-CoV-2 with important variations between those at different study sites. Living in crowded conditions was the strongest factor associated with exposure level. This study underscores the importance of providing safe, uncrowded accommodation, alongside adequate testing and public health information. FUNDING: Médecins Sans Frontières, Epicentre, Institut Pasteur's URGENCE nouveau coronavirus fund, Total Foundation.

Voluntary Community Human Immunodeficiency Virus Testing, Linkage, and Retention in Care Interventions in Kenya: Modeling the Clinical Impact and Cost-effectiveness.

Background: In southwest Kenya, the prevalence of human immunodeficiency virus (HIV) infection is about 25%. Médecins Sans Frontières has implemented a voluntary community testing (VCT) program, with linkage to care and retention interventions, to achieve the Joint United Nations Program on HIV and AIDS (UNAIDS) 90-90-90 targets by 2017. We assessed the effectiveness and cost-effectiveness of these interventions. Methods: We developed a time-discrete, dynamic microsimulation model to project HIV incidence over time in the adult population in Kenya. We modeled 4 strategies: VCT, VCT-plus-linkage to care, a retention intervention, and all 3 interventions combined. Effectiveness outcomes included HIV incidence, years of life saved (YLS), cost (2014 €), and cost-effectiveness. We performed sensitivity analyses on key model parameters. Results: With current care, the projected HIV incidence for 2032 was 1.51/100 person-years (PY); the retention and combined interventions decreased incidence to 1.03/100 PY and 0.75/100 PY, respectively. For 100000 individuals, the retention intervention had an incremental cost-effectiveness ratio (ICER) of €130/YLS compared with current care; the combined intervention incremental cost-effectiveness ratio was €370/YLS compared with the retention intervention. VCT and VCT-plus-linkage interventions cost more and saved fewer life-years than the retention and combined interventions. Baseline HIV prevalence had the greatest impact on the results. Conclusions: Interventions targeting VCT, linkage to care, and retention would decrease HIV incidence rate over 15 years in rural Kenya if planned targets are achieved. These interventions together would be more effective and cost-effective than targeting a single stage of the HIV care cascade.