Forecasting the elimination of active trachoma: An empirical model

Abstract

Background Great progress has been made toward the elimination of trachoma as a public-health problem. Mathematical and statistical models have been used to forecast when the program will attain the goal of the elimination of active trachoma, defined as prevalence of trachomatous inflammation—follicular in 1–9 year olds (TF1–9) <5%. Here we use program data to create an empirical model predicting the year of attaining global elimination of TF1–9. Methodology/Principal findings We calculated the mean number of years (95% CI) observed for an implementation unit (IU) to move from a baseline TF1–9 prevalence ≥5% to the elimination threshold, based on the region (Ethiopia vs. non-Ethiopia) and baseline prevalence category. Ethiopia IUs had significantly different rates of reaching the TF1–9 elimination threshold after a trachoma impact survey (TIS) compared to non-Ethiopia IUs across all baseline categories. We used those estimates to predict when remaining active trachoma-endemic IUs (TF1–9 ≥5%) would have their last round of mass drug administration (MDA) based on the mean number of years required and number of MDA rounds already completed. Our model predicts that elimination of TF1–9 will be achieved in 2028 in Ethiopia (95% CI: 2026–2033) and 2029 outside of Ethiopia (95% CI: 2023–2034), with some IUs in East Africa predicted to be the last requiring MDA globally. Conclusions/Significance Our empirical estimate is similar to those resulting from previous susceptible-infectious-susceptible (SIS) and mathematical models, suggesting that the forecast achievement of TF1–9 elimination is realistic with the caveat that although disease elimination progress can be predicted for most IUs, there is an important minority of IUs that is not declining or has not yet started trachoma elimination activities. These IUs represent an important barrier to the timely global elimination of active trachoma.

Modeling time to stop trachoma MDA in persistent districts of Ethiopia (Comparison of cox proportional hazard regression and machine learning models)

“…Several statistical models have been proposed to answer the above question and an inherent limitation of all models is that they assume that the future will behave like the past [22]. To estimate the mean number of rounds of MDA required to reach the active trachoma clearance threshold using classical regression models, UIs must already have achieved TF1-9 of less than 5% in an impact survey.…”

Multimodal mucosal and systemic immune characterization of a novel non-human primate trachoma model highlights the critical role of local immunity during acute phase disease

“…Given the ongoing burden of trachoma as a public health issue [1,2], it is crucial to have an accurate model for studying the disease [9,11]. Previous studies have used cynomolgus monkeys to reproduce trachoma in NHP.…”

“…Altogether, a goal of eradication (rather than elimination) would only be achieved with a vaccine. Therefore, development of a vaccine strategy seems necessary to address these pitfalls in endemic areas [9,11]. Previous vaccine strategies have passed through different preclinical models and into human trials, but with mixed results [12–15].…”

“…However, there are major drawbacks limiting long term efficacy of mass drug administration (MDA) preventive campaigns to combat trachoma. They include: i) off target antimicrobial resistance [7], ii) possible skewing of gut microbiome [8], iii) requirement of multiple rounds of treatment in some populations [5,9], iv) long term commitment of donor organizations to the control programs, v) a need for (and sometimes lack of) continued surveillance, and vi) absence of improvement in environmental and socio-economic conditions alongside control by MDA [10]. Altogether, a goal of eradication (rather than elimination) would only be achieved with a vaccine.…”

“…Altogether, a goal of eradication (rather than elimination) would only be achieved with a vaccine. Therefore, development of a vaccine strategy seems necessary to address these pitfalls in endemic areas [9,11].…”