Extensive malaria control measures have been implemented on Bioko Island, Equatorial Guinea over the past 16 years, reducing parasite prevalence and malaria-related morbidity and mortality, but without achieving elimination. Malaria vaccines offer hope for reducing the burden to zero. Three phase 1/2 studies have been conducted successfully on Bioko Island to evaluate the safety and efficacy of whole Plasmodium falciparum (Pf) sporozoite (SPZ) malaria vaccines. A large, pivotal trial of the safety and efficacy of the radiation-attenuated Sanaria® PfSPZ Vaccine against P. falciparum is planned for 2022. This study assessed the incidence of malaria at the phase 3 study site and characterized the influence of socio-demographic factors on the burden of malaria to guide trial design. A cohort of 240 randomly selected individuals aged 6 months to 45 years from selected areas of North Bioko Province, Bioko Island, was followed for 24 weeks after clearance of parasitaemia. Assessment of clinical presentation consistent with malaria and thick blood smears were performed every 2 weeks. Incidence of first and multiple malaria infections per person-time of follow-up was estimated, compared between age groups, and examined for associated socio-demographic risk factors. There were 58 malaria infection episodes observed during the follow up period, including 47 first and 11 repeat infections. The incidence of malaria was 0.25 [95% CI (0.19, 0.32)] and of first malaria was 0.23 [95% CI (0.17, 0.30)] per person per 24 weeks (0.22 in 6–59-month-olds, 0.26 in 5–17-year-olds, 0.20 in 18–45-year-olds). Incidence of first malaria with symptoms was 0.13 [95% CI (0.09, 0.19)] per person per 24 weeks (0.16 in 6–59-month-olds, 0.10 in 5–17-year-olds, 0.11 in 18–45-year-olds). Multivariate assessment showed that study area, gender, malaria positivity at screening, and household socioeconomic status independently predicted the observed incidence of malaria. Despite intensive malaria control efforts on Bioko Island, local transmission remains and is spread evenly throughout age groups. These incidence rates indicate moderate malaria transmission which may be sufficient to support future larger trials of PfSPZ Vaccine. The long-term goal is to conduct mass vaccination programmes to halt transmission and eliminate P. falciparum malaria.

中文翻译：

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赤道几内亚比奥科岛特定地区 6 个月至 45 岁儿童感染恶性疟原虫疟疾的发病率

过去 16 年来，赤道几内亚比奥科岛实施了广泛的疟疾控制措施，降低了寄生虫流行率和疟疾相关发病率和死亡率，但并未实现消除。疟疾疫苗为将负担减少到零提供了希望。已在比奥科岛成功进行了三项 1/2 期研究，以评估完整的恶性疟原虫 (Pf) 子孢子 (SPZ) 疟疾疫苗的安全性和有效性。计划于 2022 年对辐射减毒 Sanaria® PfSPZ 疫苗针对恶性疟原虫的安全性和有效性进行一项大型关键试验。该研究评估了第 3 阶段研究地点的疟疾发病率，并描述了社会人口因素的影响疟疾负担指导试验设计。从比奥科岛北比奥科省选定地区随机选择的 240 名年龄在 6 个月至 45 岁之间的个体在寄生虫血症清除后进行了 24 周的随访。每 2 周对与疟疾和厚血涂片一致的临床表现进行评估。估计每人随访时间的首次和多次疟疾感染发生率，在不同年龄组之间进行比较，并检查相关的社会人口学风险因素。在随访期间观察到 58 次疟疾感染事件，包括 47 次首次感染和 11 次重复感染。每人每 24 周疟疾的发病率为 0.25 [95% CI (0.19, 0.32)]，第一次疟疾的发病率为 0.23 [95% CI (0.17, 0.30)]（6-59 个月大的婴儿为 0.22，婴儿为 0.26 5-17 岁，18-45 岁为 0.20）。有症状的首次疟疾发病率为每人每 24 周 0.13 [95% CI (0.09, 0.19)]（6-59 个月大的儿童为 0.16，5-17 岁的儿童为 0.10，18-45-岁的儿童为 0.11）岁）。多变量评估表明，研究区域、性别、筛查时的疟疾阳性率和家庭社会经济状况独立预测了观察到的疟疾发病率。尽管在比奥科岛进行了密集的疟疾控制工作，但本地传播仍然存在，并在各个年龄段均匀传播。这些发病率表明中度疟疾传播可能足以支持 PfSPZ 疫苗未来的更大规模试验。长期目标是开展大规模疫苗接种计划，以阻止传播并消除恶性疟原虫疟疾。18-45 岁人群中有 11 人）。多变量评估表明，研究区域、性别、筛查时的疟疾阳性率和家庭社会经济状况独立预测了观察到的疟疾发病率。尽管在比奥科岛进行了密集的疟疾控制工作，但本地传播仍然存在，并在各个年龄段均匀传播。这些发病率表明中度疟疾传播可能足以支持 PfSPZ 疫苗未来的更大规模试验。长期目标是开展大规模疫苗接种计划，以阻止传播并消除恶性疟原虫疟疾。18-45 岁人群中有 11 人）。多变量评估表明，研究区域、性别、筛查时的疟疾阳性率和家庭社会经济状况独立预测了观察到的疟疾发病率。尽管在比奥科岛进行了密集的疟疾控制工作，但本地传播仍然存在，并在各个年龄段均匀传播。这些发病率表明疟疾传播中等，这可能足以支持 PfSPZ 疫苗未来的更大规模试验。长期目标是开展大规模疫苗接种计划，以阻止传播并消除恶性疟原虫疟疾。本地传播仍然存在，并在各个年龄段均匀传播。这些发病率表明中度疟疾传播可能足以支持 PfSPZ 疫苗未来的更大规模试验。长期目标是开展大规模疫苗接种计划，以阻止传播并消除恶性疟原虫疟疾。本地传播仍然存在，并在各个年龄段均匀传播。这些发病率表明中度疟疾传播可能足以支持 PfSPZ 疫苗未来的更大规模试验。长期目标是开展大规模疫苗接种计划，以阻止传播并消除恶性疟原虫疟疾。