Seroprevalence of SARS-CoV-2 Antibodies and Associated Factors in Bamako, Mali: A Population-Based Cross-Sectional Study in September 2022.

BACKGROUND: The sero-epidemiological characteristics of SARS-CoV-2 infections in Mali are not yet well understood. This study assessed SARS-CoV-2 antibody seroprevalence and factors associated with antibody responses in the general population of Bamako, the capital city and epicenter of COVID-19, to assess the magnitude of the pandemic and contribute to control strategy improvements in Mali. METHODS: A cross-sectional survey was conducted in September 2022 to collect sociodemographic information, clinical characteristics, comorbid factors, and blood samples. ELISA was performed to determine anti-Spike (anti-S) and anti-RBD antibody levels. A total of 3601 participants were enrolled in REDCap. R-Studio was used for the statistical analysis. The chi-squared (χ2) test was used to compare the proportions across different groups. Logistic regression models were used to elucidate factors associated with antibody responses. RESULT: The sex ratio for female-to-male was 3.6:1. The most representative groups were the 20-29-year-olds (28.9%, n = 1043) and the 30-39-year-olds (26.9%, n = 967). The COVID-19 vaccine coverage among the participants was 35.8%, with vaccines from Covishield AstraZeneca (13.4%), Johnson & Johnson (16.7%), Sinovac (3.9%), and BioNTech Pfizer (1.8%). Overall, S protein and RBD antibody seroprevalences were remarkably high in the study population (98% and 97%, respectively). Factors such as youth (1-9 years old) and male sex were associated with lower SARS-CoV-2 antibody responses, whereas COVID-19 vaccinations were associated with increased antibody responses. CONCLUSION: This serosurvey demonstrated the high seroprevalence of SARS-CoV-2 antibodies and highlighted the factors influencing antibody responses, while clearly underlining an underestimation of the pandemic in Mali.

Effect of a fifth round of seasonal malaria chemoprevention in children aged 5-14 years in Dangassa, an area of long transmission in Mali.

Despite a significant reduction in the burden of malaria in children under five years-old, the efficient implementation of seasonal malaria chemoprevention (SMC) at large scale remains a major concern in areas with long malaria transmission. Low coverage rate in the unattainable areas during the rainy season, a shift in the risk of malaria to older children and the rebound in malaria incidence after stopping drug administration are mainly reported in these areas. These gaps represent a major challenge in the efficient implementation of SMC measures. An open randomized study was conducted to assess the effect of a fifth additional round to current regime of SMC in older children living in Dangassa, a rural malaria endemic area. Poisson regression Model was used to estimate the reduction in malaria incidence in the intervention group compared to the control group including age groups (5-9 and 10-14 years) and the use of long-lasting insecticidal nets (LLINs; Yes or No) with a threshold at 5%. Overall, a downward trend in participation rate was observed from August (94.3%) to November (87.2%). In November (round 4), the risk of malaria incidence was similar in both groups (IRR = 0.66, 95%CI [0.35-1.22]). In December (round 5), a decrease of 51% in malaria incidence was observed in intervention group compared to control group adjusted for age groups and the use of LLINs (IRR = 0.49, 95%CI [0.26-0.94]), of which 17% of reduction is attributable to the 5th round in the intervention group. An additional fifth round of SMC resulted in a significant reduction of malaria incidence in the intervention group. The number of SMC rounds could be adapted to the local condition of malaria transmission.