ABSTRACT
OBJECTIVES: When malaria vectors consume ivermectin in a blood meal, their survival probability decreases, potentially reducing malaria transmission during mass drug administrations. However, questions remain regarding the optimal dosing. This study aimed to compare the mosquitocidal effect and pharmacokinetics of two-dose regimens of ivermectin for malaria vector control. DESIGN: We conducted an open-label randomized control trial in Kenya, staggered in blocks with sequential intervention groups and parallel controls. Participants were randomly assigned (2:1:1:1) using computer random-sequence generation, unstratified, with one block of six pharmacokinetics-only participants (single-dose ivermectin) and six blocks of four participants (3:1 intervention vs control), to receive single-dose ivermectin (400 mcg/kg, n = 12), three daily doses (3-day regimen 300 mcg/kg, n = 6), albendazole (400 mg, n = 6), or no treatment (negative control, n = 6). Our primary outcome was Anopheles gambiae survival (time-to-event [days]) after blood feeding up to 10 days after drug administration. We also evaluated pharmacokinetics (peak plasma and capillary blood concentration, areas under the plasma and capillary blood concentration-time curve from time of last administration to time of last observation, time to reach peak plasma and capillary blood concentration, terminal elimination half-life) up to 7 days after treatment. RESULTS: A total of 36 healthy volunteers aged 21-32 years were recruited into the study and followed up to completion, with two participants not attending the visit on day 28. All drug regimens were well-tolerated. Both regimens showed significant mosquitocidal effect in the first 7 days. At 10 days after treatment, the single dose presented superior longevity of effect (adjusted hazard ratio = 3.91; 95% confidence interval = 1.93-7.93; P <0.001) compared with the triple dose (adjusted hazard ratio = 1.79; 95% confidence interval = 0.88-3.62; P = 0.0.11). Albendazole had, overall, no mosquitocidal effect. CONCLUSIONS: It is unclear why a single dose led to increased bio-efficacy compared with a triple dose. We recommend trials investigating ivermectin mass drug administrations for malaria control to consider single-dose ivermectin. A single-dose regimen is also expected to present additional operational advantages compared with a 3-day regimen, leading to improved programmatic suitability.
ABSTRACT
Background: There are limited data on the immunogenicity of coronavirus disease 2019 (COVID-19) vaccines in African populations. Here we report the immunogenicity and safety of the ChAdOx1 nCoV-19 (AZD1222) vaccine from a phase 1/2 single-blind, randomised, controlled trial among adults in Kenya conducted as part of the early studies assessing vaccine performance in different geographical settings to inform Emergency Use Authorisation. Methods: We recruited and randomly assigned (1:1) 400 healthy adults aged ≥18 years in Kenya to receive ChAdOx1 nCoV-19 or control rabies vaccine, each as a two-dose schedule with a 3-month interval. The co-primary outcomes were safety, and immunogenicity assessed using total IgG enzyme-linked immunosorbent assay (ELISA) against SARS-CoV-2 spike protein 28 days after the second vaccination. Results: Between 28 th October 2020 and 19 th August 2021, 400 participants were enrolled and assigned to receive ChAdOx1 nCoV-19 (n=200) or rabies vaccine (n=200). Local and systemic adverse events were self-limiting and mild or moderate in nature. Three serious adverse events were reported but these were deemed unrelated to vaccination. The geometric mean anti-spike IgG titres 28 days after second dose vaccination were higher in the ChAdOx1 group (2773 ELISA units [EU], 95% CI 2447, 3142) than in the rabies vaccine group (61 EU, 95% CI 45, 81) and persisted over the 12 months follow-up. We did not identify any symptomatic infections or hospital admissions with respiratory illness and so vaccine efficacy against clinically apparent infection could not be measured. Vaccine efficacy against asymptomatic SARS-CoV-2 infection was 38.4% (95% CI -26.8%, 70.1%; p=0.188). Conclusions: The safety, immunogenicity and efficacy against asymptomatic infection of ChAdOx1 nCoV-19 among Kenyan adults was similar to that observed elsewhere in the world, but efficacy against symptomatic infection or severe disease could not be measured in this cohort. Pan-African Clinical Trials Registration: PACTR202005681895696 (11/05/2020).
ABSTRACT
BACKGROUND: In sub-Saharan Africa, data on virologic outcomes of young people living with HIV (YLWH) enrolled on antiretroviral therapy (ART) remains scarce. In this study, we describe the prevalence of HIV virological non-suppression (VNS) and its associated factors among YLWH aged 18-24 years from the Kenyan coast. METHODS: Data were analyzed for 384 YLWH who participated in a larger cross-sectional study conducted between November 2018 and September 2019 in two counties at the Kenyan coast (Kilifi and Mombasa). Descriptive statistics were used to summarize sample characteristics and logistic regression was used for statistical modeling of factors associated with VNS. In this study, VNS was defined as plasma viral load ≥ 1000 copies/mL. RESULTS: Among these YLWH with a mean age of 20.7 years (SD = 2.2); 55.5% females, the overall prevalence of VNS was 32.0% (95% Confidence interval (95% CI): 27.5, 36.9%). In the multivariable logistic regression analysis, being from a largely rural setting (adjusted Odds Ratio (aOR) 1.73, 95% CI 1.10, 2.71; p = 0.02), underweight (aOR 1.87, 95% CI 1.16, 3.01; p = 0.01) and low self-reported ART adherence (aOR 2.83, 95% CI 1.34, 6.00; p = 0.01) were significantly associated with higher odds of VNS in YLWH. CONCLUSIONS: In this study, high levels of VNS were observed among YLWH and this was significantly associated with rural residency, nutritional and ART adherence problems. ART adherence counselling and nutritional support and education should be intensified in this setting targeting YLWH residing mostly in rural areas. Given the high frequency of VNS, there is need to closely monitor viral load and profile HIV drug resistance patterns in youths from the Kenyan coast with confirmed virologic failure. The latter will help understand whether drug resistance also contributes to poor viral suppression in addition to, or exclusive of suboptimal ART adherence.