District-Level Forecast of Achieving Trachoma Elimination as a Public Health Problem By 2030: An Ensemble Modelling Approach

Assessing the feasibility of 2030 as a target date for global elimination of trachoma, and identification of districts that may require enhanced treatment to meet World Health Organization (WHO) elimination criteria by this date are key challenges in operational planning for trachoma programmes. Here we address these challenges by prospectively evaluating forecasting models of trachomatous inflammation-follicular (TF) prevalence, leveraging ensemble-based approaches. Seven candidate probabilistic models were developed to forecast district-wise TF prevalence in 11 760 districts, trained using district-level data on the population prevalence of TF in children aged 1-9 years from 2004 to 2022. Geographical location, history of mass drug administration treatment, and previously measured prevalence data were included in these models as key predictors. The best-performing models were included in an ensemble, using weights derived from their relative likelihood scores. To incorporate the inherent stochasticity of disease transmission and challenges of population-level surveillance, we forecasted probability distributions for the TF prevalence in each geographic district, rather than predicting a single value. Based on our probabilistic forecasts, 1.46% (95% confidence interval [CI]: 1.43-1.48%) of all districts in trachoma-endemic countries, equivalent to 172 districts, will exceed the 5% TF control threshold in 2030 with the current interventions. Global elimination of trachoma as a public health problem by 2030 may require enhanced intervention and/or surveillance of high-risk districts.

Simplified dosing of oral azithromycin for children 1-11 months old in child survival programmes: age-based and height-based dosing protocols

BACKGROUND

To facilitate mass distribution of azithromycin, trachoma control programmes use height instead of weight to determine dose for children 6 months to 15 years old. WHO has recommended azithromycin distribution to children 1-11 months old to reduce mortality in high mortality settings under carefully monitored conditions. Weight was used to determine dose in children 1-5 months old in studies of azithromycin distribution for child survival, but a simplified approach using age or height for all aged 1-11 months old could increase programme efficiency in real-world settings.

METHODS

This secondary analysis used data from two cluster randomised trials of azithromycin distribution for child mortality in Niger and Burkina Faso. An exhaustive search algorithm was developed to determine the optimal dose for different age groups, using tolerance limits of 10-20 mg/kg for children 1-2 months old and 15-30 mg/kg for children 3-11 months old. Height-based dosing was evaluated against the existing trachoma dosing pole and with a similar exhaustive search.

RESULTS

The optimal two-tiered age-based approach suggested a dose of 80 mg (2 mL) for children 1-2 months old and 160 mg (4 mL) for children 3-11 months old. Under this schedule, 89%-93% of children would have received doses within tolerance limits in both study populations. Accuracy was 93%-94% with a three-tiered approach, which resulted in doses of 80 mg (2 mL), 120 mg (3 mL) and 160 mg (4 mL) for children 1-2, 3-4 and 5-11 months old, respectively. For children 1-5 months old, the existing height pole would result in 70% of doses within tolerance limits. The optimisation identified height-based dosing options with 95% accuracy, although this would require changes to the existing dosing pole as well as additional training to measure infants lying flat.

CONCLUSIONS

Overall, an age-based approach with two age tiers resulted in high accuracy while considering both concerns about overdosing in this young population and simplicity of field operations.

Forecasting the elimination of active trachoma: An empirical model

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.

OUP accepted manuscript

Background

The International Trachoma Initiative (ITI) provides azithromycin for mass drug administration (MDA) to eliminate trachoma as a public health problem. Azithromycin is given as tablets for adults and powder for oral suspension (POS) is recommended for children aged <7 y, children <120 cm in height (regardless of age) or anyone who reports difficulty in swallowing tablets. An observational assessment of MDA for trachoma was conducted to determine the frequency with which children aged 6 mo through 14 y received the recommended dose and form of azithromycin according to current dosing guidelines and to assess risk factors for choking and adverse swallowing events (ASEs).

Methods

MDA was observed in three regions of Ethiopia and data were collected on azithromycin administration and ASEs.

Results

A total of 6477 azithromycin administrations were observed; 97.9% of children received the exact recommended dose. Of children aged 6 mo to <7 y or <120 cm in height, 99.6% received POS. One child experienced choking and 132 (2%) experienced ≥1 ASEs. Factors significantly associated with ASEs included age 6–11 mo or 1–6 y, non-calm demeanor and requiring coaxing prior to drug administration.

Conclusions

There is a high level of adherence to the revised azithromycin dosing guidelines and low incidence of choking and ASEs.

Use of modelling to modify trachoma elimination strategies affected by the COVID-19 pandemic

Models predict that the negative effects of delayed implementation in trachoma elimination programmes caused by the COVID-19 pandemic will be minimal, except in high prevalence districts where progress may be reversed. During times of change we must stand by our principles of evidence-based decision-making, but also be willing to show flexibility. Slow progress to elimination in high prevalence districts was already a significant challenge to the global programme and mitigation of COVID-related delays with enhanced implementation provides an opportunity to simultaneously address an unprecedented challenge and a pre-existing one.

Trachoma Prevalence After Discontinuation of Mass Azithromycin Distribution

Background

As the World Health Organization seeks to eliminate trachoma by 2020, countries are beginning to control the transmission of trachomatous inflammation–follicular (TF) and discontinue mass drug administration (MDA) with oral azithromycin. We evaluated the effect of MDA discontinuation on TF_1–9 prevalence at the district level.

Methods

We extracted from the available data districts with an impact survey at the end of their program cycle that initiated discontinuation of MDA (TF_1–9 prevalence <5%), followed by a surveillance survey conducted to determine whether TF_1–9 prevalence remained below the 5% threshold, warranting discontinuation of MDA. Two independent analyses were performed, 1 regression based and 1 simulation based, that assessed the change in TF_1–9 from the impact survey to the surveillance survey.

Results

Of the 220 districts included, TF_1–9 prevalence increased to >5% from impact to surveillance survey in 9% of districts. Regression analysis indicated that impact survey TF_1–9 prevalence was a significant predictor of surveillance survey TF_1–9 prevalence. The proportion of simulations with >5% TF_1–9 prevalence in the surveillance survey was 2%, assuming the survey was conducted 4 years after MDA.

Conclusion

An increase in TF_1–9 prevalence may represent disease resurgence but could also be due to measurement error. Improved diagnostic tests are crucial to elimination of TF_1–9 as a public health problem.

Quality Assurance and Quality Control in the Global Trachoma Mapping Project

In collaboration with the health ministries that we serve and other partners, we set out to complete the multiple-country Global Trachoma Mapping Project. To maximize the accuracy and reliability of its outputs, we needed in-built, practical mechanisms for quality assurance and quality control. This article describes how those mechanisms were created and deployed. Using expert opinion, computer simulation, working groups, field trials, progressively accumulated in-project experience, and external evaluations, we developed 1) criteria for where and where not to undertake population-based prevalence surveys for trachoma; 2) three iterations of a standardized training and certification system for field teams; 3) a customized Android phone–based data collection app; 4) comprehensive support systems; and 5) a secure end-to-end pipeline for data upload, storage, cleaning by objective data managers, analysis, health ministry review and approval, and online display. We are now supporting peer-reviewed publication. Our experience shows that it is possible to quality control and quality assure prevalence surveys in such a way as to maximize comparability of prevalence estimates between countries and permit high-speed, high-fidelity data processing and storage, while protecting the interests of health ministries.

Antimicrobial resistance following mass azithromycin distribution for trachoma: a systematic review

Mass azithromycin distribution is a core component of trachoma control programmes and could reduce mortality in children younger than 5 years in some settings. In this systematic review we synthesise evidence on the emergence of antimicrobial resistance after mass azithromycin distribution. We searched electronic databases for publications up to June 14, 2018. We included studies of any type (excluding modelling studies, surveillance reports, and review articles) on community-wide distribution of oral azithromycin for the prevention and treatment of trachoma that assessed macrolide resistance, without restrictions to the type of organism. We extracted prevalence of resistance from published reports and requested unpublished data from authors of included studies. Of 213 identified studies, 19 met inclusion criteria (12 assessed Streptococcus pneumoniae) and were used for qualitative synthesis. Macrolide resistance after azithromycin distribution was reported in three of the five organisms studied. The lack of resistance in Chlamydia trachomatis suggests that azithromycin might remain effective for trachoma programmes, but evidence is scarce. As mass azithromycin distribution for trachoma continues and is considered for other indications, ongoing monitoring of antimicrobial resistance will be required.

Peripheral blood stem cell transplantation

Peripheral blood stem cell (PBSC) transplantation is a promising new therapy in the treatment of malignancies. It is being used to supplement and in place of bone marrow transplantation to restore hematopoiesis after myeloablative therapy. PBSCs are collected through apheresis, generally after a course of myelosuppressive therapy to prime the progenitor cells. Problems that potentially could arise during PBSC collection include citrate toxicity, hypovolemia, and thrombocytopenia. PBSC infusion is similar to the infusion of bone marrow. Engraftment following PBSC transplantation progresses rapidly, resulting in shorter hospital stays. The future of PBSC therapy looks promising, but much still has to be learned about this innovative treatment.