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Background <p>Mass drug administration (MDA) achieved sustained malaria elimination on Mohéli and Anjouan but only transient control on Grande Comore. Following resurgence from 1061 cases in 2015 to 19,453 in 2018, a renewed MDA campaign was implemented on Grande Comore in 2019. This study evaluates its effectiveness compared to the 2013 campaign to identify determinants of sustained suppression.</p> Methods <p>Two rounds of artemisinin‑piperaquine plus single low‑dose primaquine were administered in September–October 2019, targeting 348,961 residents. MDA coverage, adverse events, and parasitological outcomes from surveys at four time points were assessed. Monthly confirmed cases from 2012–2024 were analyzed descriptively to compare the epidemiological trajectories following the 2013 and 2019 campaigns, acknowledging that this historical comparison with multiple co‑varying confounders does not permit causal attribution.</p> Results <p>Round 1 coverage was 83.5%, declining to 58.0% in Round 2 (<i>p</i> = 0.0008). Adverse events occurred in 0.3% of doses, with no severe events reported. Parasitemia declined by 92.7% after Round 1 and remained 96.5% below baseline at 15&#xa0;months. Reported monthly cases declined by 79.7% from the pre‑MDA mean (1,731 cases/month) to the early post‑MDA mean (352 cases/month), reaching a nadir of 192 cases in April 2020—an 88.2% reduction from baseline (1,621 cases/month). However, this nadir coincided with the first COVID‑19 lockdown, which likely reduced healthcare access and reporting completeness. Cases remained below the 50% threshold (810 cases/month) for 19 consecutive months but rebounded to 53.7% above baseline by 2022–2024. In descriptive comparison with the 2013 campaign (99.1% reduction, &gt; 48&#xa0;months suppression), the 2019 campaign showed a lower reduction (88.2%) and shorter suppression duration (19&#xa0;months). Spatially, resurgence after the 2013 campaign was relatively focal, while after the 2019 campaign it became more widespread—a pattern consistent with a larger or more dispersed residual parasite reservoir.</p> Conclusions <p>The 2019 MDA was followed by less durable suppression than observed after the 2013 campaign. Declining second‑round coverage, weaker post‑MDA surveillance, and COVID‑19‑related disruptions may have contributed, but the historical comparison involves multiple confounders and precludes causal attribution. These findings should be interpreted as hypothesis‑generating for future malaria elimination strategies.</p> <p><i>Trial registration</i> The study protocol was approved by the National Health Ethics Committee of the Union of Comoros (No. 12521/MSSPG/CAB) on 13 September 2012, the Guangzhou University of Chinese Medicine Ethics Committee for Health Research (No. 2012L0816) on 25 September 2012, and the Ethical Board of Guangdong Provincial Hospital of Chinese Medicine (No. BF2019-169-01) on 18 October 2019.</p>

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From near-elimination to resurgence: a comparative analysis of two mass drug administration campaigns on Grande Comore Island (2013–2024)

  • 期刊论文

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  • 发表日期：

    2026年8月4日

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  • Mingqiang Li,
  • Yueming Yuan,
  • Hongying Zhang,
  • Chenguang Lu,
  • Ruimei Liu,
  • Lei Shu,
  • Wei Xie,
  • Ruixiang Tan,
  • Kamal Said Abdallah,
  • Wanting Wu,
  • Salim Abdoulkarim Mmadi,
  • Zhengjie Yu,
  • Affane Bacar,
  • Weihe Chen,
  • Nadia Julie,
  • Jianping Song,
  • Changsheng Deng,
  • Guoming Li

摘要

Background

Mass drug administration (MDA) achieved sustained malaria elimination on Mohéli and Anjouan but only transient control on Grande Comore. Following resurgence from 1061 cases in 2015 to 19,453 in 2018, a renewed MDA campaign was implemented on Grande Comore in 2019. This study evaluates its effectiveness compared to the 2013 campaign to identify determinants of sustained suppression.

Methods

Two rounds of artemisinin‑piperaquine plus single low‑dose primaquine were administered in September–October 2019, targeting 348,961 residents. MDA coverage, adverse events, and parasitological outcomes from surveys at four time points were assessed. Monthly confirmed cases from 2012–2024 were analyzed descriptively to compare the epidemiological trajectories following the 2013 and 2019 campaigns, acknowledging that this historical comparison with multiple co‑varying confounders does not permit causal attribution.

Results

Round 1 coverage was 83.5%, declining to 58.0% in Round 2 (p = 0.0008). Adverse events occurred in 0.3% of doses, with no severe events reported. Parasitemia declined by 92.7% after Round 1 and remained 96.5% below baseline at 15 months. Reported monthly cases declined by 79.7% from the pre‑MDA mean (1,731 cases/month) to the early post‑MDA mean (352 cases/month), reaching a nadir of 192 cases in April 2020—an 88.2% reduction from baseline (1,621 cases/month). However, this nadir coincided with the first COVID‑19 lockdown, which likely reduced healthcare access and reporting completeness. Cases remained below the 50% threshold (810 cases/month) for 19 consecutive months but rebounded to 53.7% above baseline by 2022–2024. In descriptive comparison with the 2013 campaign (99.1% reduction, > 48 months suppression), the 2019 campaign showed a lower reduction (88.2%) and shorter suppression duration (19 months). Spatially, resurgence after the 2013 campaign was relatively focal, while after the 2019 campaign it became more widespread—a pattern consistent with a larger or more dispersed residual parasite reservoir.

Conclusions

The 2019 MDA was followed by less durable suppression than observed after the 2013 campaign. Declining second‑round coverage, weaker post‑MDA surveillance, and COVID‑19‑related disruptions may have contributed, but the historical comparison involves multiple confounders and precludes causal attribution. These findings should be interpreted as hypothesis‑generating for future malaria elimination strategies.

Trial registration The study protocol was approved by the National Health Ethics Committee of the Union of Comoros (No. 12521/MSSPG/CAB) on 13 September 2012, the Guangzhou University of Chinese Medicine Ethics Committee for Health Research (No. 2012L0816) on 25 September 2012, and the Ethical Board of Guangdong Provincial Hospital of Chinese Medicine (No. BF2019-169-01) on 18 October 2019.