Current and future trends in tuberculosis incidence in New York City: a dynamic modelling analysis

Background: After steady decline since the 1990s, tuberculosis incidence in New York City and throughout the USA has plateaued. We aimed to explore the major drivers of the flattening of tuberculosis incidence in New York City and to project the future trajectory of the tuberculosis epidemic in the absence of any additional intervention. Methods: We developed a compartmental transmission model of tuberculosis in New York City. The model was parameterised with detailed epidemiological data and stratified by age and nativity (US-born vs foreign-born). We ran the model under five alternative scenarios representing different explanations for recent declines in tuberculosis incidence. We evaluated the relative likelihood of each scenario by comparing its output with available data. We used the most likely scenarios to explore potential mechanisms underlying the recent declines in tuberculosis in New York City and to describe the reasonable range of future epidemic trajectories. Our primary outcome was the projected rate of decline in tuberculosis incidence from 2015 to 2025. Model calibration yielded estimates of future disease incidence and reductions in incidence with 95% credible intervals (CrIs). Findings: Demographic changes and declining tuberculosis transmission alone were insufficient to explain recent trends in tuberculosis incidence in New York City. Only scenarios that assumed contemporary changes in tuberculosis dynamics among foreign-born individuals—a declining rate of reactivation or a decrease in imported subclinical tuberculosis—could accurately describe the trajectory of disease incidence since 2007. In those scenarios, the projected decline in incidence from 2015 to 2025 varied from minimal (2·0% per year [95% CrI 0·4–3·5]) to similar to 2005 to 2009 trends (4·4% per year [2·5–6·4]). The primary factor differentiating optimistic from pessimistic projections was the degree to which improvements in tuberculosis dynamics among the foreign-born population continued into the coming decade. Interpretation: Further progress towards elimination of tuberculosis in New York City requires additional focus on the foreign-born population. Without additional intervention in this group, tuberculosis incidence might not decline further. Funding: None

Effectiveness of one dose of oral cholera vaccine in response to an outbreak: a case-cohort study

Background: Oral cholera vaccines represent a new effective tool to fight cholera and are licensed as two-dose regimens with 2–4 weeks between doses. Evidence from previous studies suggests that a single dose of oral cholera vaccine might provide substantial direct protection against cholera. During a cholera outbreak in May, 2015, in Juba, South Sudan, the Ministry of Health, Médecins Sans Frontières, and partners engaged in the first field deployment of a single dose of oral cholera vaccine to enhance the outbreak response. We did a vaccine effectiveness study in conjunction with this large public health intervention. Methods: We did a case-cohort study, combining information on the vaccination status and disease outcomes from a random cohort recruited from throughout the city of Juba with that from all the cases detected. Eligible cases were those aged 1 year or older on the first day of the vaccination campaign who sought care for diarrhoea at all three cholera treatment centres and seven rehydration posts throughout Juba. Confirmed cases were suspected cases who tested positive to PCR for Vibrio cholerae O1. We estimated the short-term protection (direct and indirect) conferred by one dose of cholera vaccine (Shanchol, Shantha Biotechnics, Hyderabad, India). Findings: Between Aug 9, 2015, and Sept 29, 2015, we enrolled 87 individuals with suspected cholera, and an 898-person cohort from throughout Juba. Of the 87 individuals with suspected cholera, 34 were classified as cholera positive, 52 as cholera negative, and one had indeterminate results. Of the 858 cohort members who completed a follow-up visit, none developed clinical cholera during follow-up. The unadjusted single-dose vaccine effectiveness was 80·2% (95% CI 61·5–100·0) and after adjusting for potential confounders was 87·3% (70·2–100·0). Interpretation: One dose of Shanchol was effective in preventing medically attended cholera in this study. These results support the use of a single-dose strategy in outbreaks in similar epidemiological settings. Funding: Médecins Sans Frontières

Feasibility of achieving the 2025 WHO global tuberculosis targets in South Africa, China, and India: a combined analysis of 11 mathematical models

Background: The post-2015 End TB Strategy proposes targets of 50% reduction in tuberculosis incidence and 75% reduction in mortality from tuberculosis by 2025. We aimed to assess whether these targets are feasible in three high-burden countries with contrasting epidemiology and previous programmatic achievements. Methods: 11 independently developed mathematical models of tuberculosis transmission projected the epidemiological impact of currently available tuberculosis interventions for prevention, diagnosis, and treatment in China, India, and South Africa. Models were calibrated with data on tuberculosis incidence and mortality in 2012. Representatives from national tuberculosis programmes and the advocacy community provided distinct country-specific intervention scenarios, which included screening for symptoms, active case finding, and preventive therapy. Findings: Aggressive scale-up of any single intervention scenario could not achieve the post-2015 End TB Strategy targets in any country. However, the models projected that, in the South Africa national tuberculosis programme scenario, a combination of continuous isoniazid preventive therapy for individuals on antiretroviral therapy, expanded facility-based screening for symptoms of tuberculosis at health centres, and improved tuberculosis care could achieve a 55% reduction in incidence (range 31–62%) and a 72% reduction in mortality (range 64–82%) compared with 2015 levels. For India, and particularly for China, full scale-up of all interventions in tuberculosis-programme performance fell short of the 2025 targets, despite preventing a cumulative 3·4 million cases. The advocacy scenarios illustrated the high impact of detecting and treating latent tuberculosis. Interpretation: Major reductions in tuberculosis burden seem possible with current interventions. However, additional interventions, adapted to country-specific tuberculosis epidemiology and health systems, are needed to reach the post-2015 End TB Strategy targets at country level. Funding: Bill and Melinda Gates Foundatio