Adapting malaria indicator surveys to investigate treatment adherence: a pilot study on Bioko Island, Equatorial Guinea.

BACKGROUND: Adherence to anti-malarial treatment regimens is an important aspect of understanding and improving the impact of malaria case management. However, both adherence to artemisinin-based combination therapy (ACT) and the factors driving it vary widely. While many other evaluation activities have been conducted on Bioko Island, until now adherence to anti-malarial treatments, and in particular ACT has not been evaluated. METHODS: The implementation of a malaria indicator survey (MIS) conducted on Bioko in 2023 was leveraged to evaluate adherence to ACT provided to individuals testing positive following the survey. A follow-up team visited the targeted households, physically observed treatment blisters where possible, and provided messaging to household members on the importance of adhering to the treatment guidelines to household members. The team used survey data from the targeted households to make messaging as relevant to the household's particular context as possible. RESULTS: Overall ACT adherence on Bioko Island was low, around 50%, and this varied demographically and geographically. Some of the highest transmission areas had exceptionally low adherence, but no systematic relationship between proper adherence and Plasmodium falciparum prevalence was detected. Estimates of adherence from follow-up visits were much lower than survey-based estimates in the same households (52.5% versus 87.1%), suggesting that lack of proper adherence may be a much larger issue on Bioko Island than previously thought. CONCLUSION: Representative surveys can be easily adapted to provide empirical estimates of adherence to anti-malarial treatments, complementary to survey-based and health facility-based estimates. The large discrepancy between adherence as measured in this study and survey-based estimates on Bioko Island suggests a health facility-based study to quantify adherence among the population receiving treatment for symptomatic malaria may be necessary.

Evolution of pfhrp2 and pfhrp3 deletions in Equatorial Guinea between the pre- and post-RDT introduction.

BACKGROUND: Pfhrp2 and pfhrp3 deletions are threatening Plasmodium falciparum malaria diagnosis by rapid diagnostic tests (RDT) due to false negatives. This study assesses the changes in the frequencies of pfhrp2 and pfhrp3 deletions (pfhrp2Del and pfhrp3Del, respectively) and the genes in their flaking regions, before and after RDT introduction in Equatorial Guinea. METHODS: A total of 566 P. falciparum samples were genotyped to assess the presence of pfhrp2 and pfhrp3 deletions and their flanking genes. The specimens were collected 18 years apart from two provinces of Equatorial Guinea, North Bioko (Insular Region) and Litoral Province (Continental Region). Orthologs of pfhrp2 and pfhrp3 genes from other closely related species were used to compare sequencing data to assess pfhrp2 and pfhrp3 evolution. Additionally, population structure was studied using seven neutral microsatellites. RESULTS: This study found that pfhrp2Del and pfhrp3Del were present before the introduction of RDT; however, they increased in frequency after their use, reaching more than 15%. Haplotype networks suggested that pfhrp2Del and pfhrp3Del emerged multiple times. Exon 2 of pfhrp2 and pfhrp3 genes had high variability, but there were no significant changes in amino acid sequences. CONCLUSIONS: Baseline sampling before deploying interventions provides a valuable context to interpret changes in genetic markers linked to their efficacy, such as the dynamic of deletions affecting RDT efficacy.

The Use of a Theory of Change Model to Guide the Implementation of a Comprehensive Surgical Specialty Training Program in Equatorial Guinea.

Background: Equatorial Guinea (EG) is located on the African west coast, with only 0.4 trained physicians per 1,000 resident population. The country has one medical school and there is no specialist training program. From 2000 to 2022, 524 doctors have received their medical degree. However, the number of national surgical specialists in the entire country is currently 42. Objective: Formación Especializada Sanitaria en Guinea Ecuatorial (FES Guinea) is a program specifically aimed at designing and implementing a long-term national surgical specialist training program. Methods: Más Que Salud (+QS), which means "More than Health" in Spanish, is a nonprofit organization leading the FES Guinea program. We used the theory of change (ToC) framework to evaluate the work accomplished and implement subsequent phases. The initial phase (A) included a needs assessment and mapping of available resources. An intermediate phase (B) started with a memorandum of understanding to implement a Train the Trainer program. The consolidation phase (C) consists of educational interventions and future advanced training projects. Findings: The ToC model allowed us an analyses of initial and intermediate phases. The needs assessments and resources mapping were executed while several scientific meetings and workshops were given. Scholarships to support specialist training abroad benefited six physicians in a diverse set of surgical disciplines. A regulatory commission to implement the FES Guinea program and the National Medical Council of EG were created. Working directly with the EG Ministry of Health, +QS codesigned a National Health Development Plan that began implementation in 2021 to continue until 2025. Conclusions: The ToC model allowed us to predict the current and future potential effects of FES Guinea on surgical workforce development in EG. This is a unique surgical training program, which combined effective initiatives spearheaded initially by an NGO that successfully incorporated both local health and academic authorities, ensuring sustainability.

Knowledge, attitudes, and practices related to soil-transmitted helminth infections among residents of Bata district, Equatorial Guinea; a cross-sectional study.

BACKGROUND: Soil-transmitted helminth (STH) infection control remains a priority in endemic regions where local epidemiological data are needed for sustainable control strategies, particularly regarding population knowledge, attitudes, and practices (KAP). Our work assessed KAP toward STH infection and associated factors among residents of Bata district, Equatorial Guinea. METHODS: A community-based cross-sectional study was conducted among 14 randomly selected communities in the Bata district. Eligible participants were interviewed face-to-face using a standardized questionnaire. Participants aged under 18 years were interviewed in the presence of their parents or legal guardians. For participants aged less than ten, a simplified version of the main questionnaire was developed focusing on children's practices toward STH and was administered to their parents or legal guardians. RESULTS: A total of 399 participants were included in the present analysis. Among them, 58% responded to the main questionnaire. The mean (± SD) age of participants aged 10 and over was 37.5 (± 22.2) years, and 60% of them were females, while the mean (± SD) age of those aged less than ten was 5.0 (± 2.5) years. The respondents' overall knowledge, attitudes, and practices to STH were rated as bad (33%), very good (77%), and good (55%), respectively. Knowledge was significantly associated with education level (p = 0.04) with the knowledge level lower for participants with no formal education than for those with secondary/university education (ß = -0.56, 95% CI: -1.00 - -0.12, p = 0.01); Appropriate attitudes level was significantly associated with occupation (p = 0.02) and education levels (p = 0.049) with the appropriate attitude level lower for students than for farmers/fishers (ß = -1.24, 95% CI: -2.17--0.32, p = 0.01) and for primary-level participants than for those with secondary/university education (ß = -0.68, 95% CI: -1.23--0.13, p = 0.02); while appropriate practice level were significantly associated with age (p = 0.01), occupation (p = 0.01), and education (p = 0.02), with the appropriate practices level increasing with age (ß = 0.03, 95% CI: 0.005 - 0.05, p = 0.01) and lower in participants with no formal education than in those with secondary/university education (ß = -1.19, -2.05 - -0.32, p = 0.007). CONCLUSION: The present study revealed a lack of knowledge about STH in the study population, particularly regarding disease causes and transmission ways, highlighting the need for the implementation of integrated health education strategies, both at the community and school levels.

HIV diagnosis in Equatorial Guinea. Keys to reduce the diagnostic and therapeutic delay.

BACKGROUND: In Equatorial Guinea, only 54 % of people living with HIV know their HIV status. There are no confirmatory or molecular diagnostic techniques for early diagnosis or monitoring of infection in the country. Rapid diagnostic tests can induce false-positive diagnoses if used as a confirmatory technique. Our study aimed to identify the challenges of early HIV diagnosis in Equatorial Guinea by analyzing the rate of false positive diagnoses, diagnostic and therapeutic delays, and treatment failures among those on antiretroviral therapy. METHODS: From 2019-2022, dried blood from 341 children, adolescents and adults diagnosed in Equatorial Guinea as HIV-positive by rapid diagnostic testing, and from 54 HIV-exposed infants were collected in Bata and sent to Madrid to confirm HIV-infection by molecular (Xpert HIV-1Qual, Cepheid) and/or serological confirmatory assays (Geenius-HIV-1/2, BioRad). HIV diagnostic delay (CD4 <350cells/mm3), advanced disease at diagnosis (CD4 <200cells/mm3) and antiretroviral treatment delay and failure (viraemia >1,000RNA-HIV-1-copies/ml) were also studied after viral quantification (XpertVL HIV-1, Cepheid). RESULTS: False-positive diagnoses were identified in 5 % of analysed samples. HIV infection was confirmed in 90.5 % of previously diagnosed patients in Equatorial Guinea and 3.7 % of HIV-exposed children undiagnosed in the field. Two-thirds of each new HIV patient had delayed diagnosis, and one-third had advanced disease. Treatment delay occurred in 28.3 % of patients, being around four times more likely in adolescents/adults than children. More than half (56 %) of 232 treated patients presented treatment failure, being significantly higher in children/adolescents than in adults (82.9 %/90 % vs. 45.6 %, p < 0.001). CONCLUSION: We identified some challenges of early HIV diagnosis in Equatorial Guinea, revealing a high rate of false positive diagnoses, diagnostic/treatment delays, and treatment failures that need to be addressed. The implementation of more accurate rapid diagnostic techniques and confirmatory tests, along with improving access to care, treatment, awareness, and screening, would contribute to controlling the spread of HIV in the country.

A paradigm for Africa-centric vaccine development in Equatorial Guinea.

The Equatorial Guinea Malaria Vaccine Initiative (EGMVI) highlights how long-term African government and international energy industry investment, plus novel partnerships, can enable clinical development of vaccines in Africa, for Africa. We review achievements and challenges of this pioneering, award-winning, public-private partnership which offers a model for future Africa-centric clinical research and development (R&D).

[Single - nucleotide polymorphisms of artemisinin resistance - related Pfubp1 and Pfap2mu genes in Bioko Island, Equatorial Guinea from 2018 to 2020].

OBJECTIVE: To investigate the prevalence of single nucleotide polymorphisms (SNPs) of artemisinin resistance-related Pfubp1 and Pfap2mu genes in Plasmodium falciparum isolates from Bioko Island, Equatorial Guinea, so as to to provide baseline data for the formulation of malaria control strategies in Bioko Island. METHODS: A total of 184 clinical blood samples were collected from patients with P. falciparum malaria in Bioko Island, Equatorial Guinea from 2018 to 2020, and genomic DNA was extracted. The Pfubp1 and Pfap2mu gene SNPs of P. falciparum were determined using a nested PCR assay and Sanger sequencing, and the gene sequences were aligned. RESULTS: There were 159 wild-type P. falciparum isolates (88.83%) from Bioko Island, Equatorial Guinea, and 6 SNPs were identified in 20 Pfubp1-mutant P. falciparum isolates (11.17%), in which 4 non-synonymous mutations were detected, including E1516G, K1520E, D1525E, E1528D. There was only one Pfubp1gene mutation site in 19 Pfubp1-mutant P. falciparum isolates (95.00%), in which non-synonymous mutations accounted for 68.42% (13/19). D1525E and E1528D were identified as major known epidemic mutation sites in the Pfubp1 gene associated with resistance to artemisinin-based combination therapies (ACTs). At amino acid position 1525, there were 178 wild-type P. falciparum isolates (99.44%) and 1 mutant isolate (0.56%), with such a mutation site identified in blood samples in 2018, and at amino acid position 1528, there were 167 wild-type P. falciparum isolates (93.30%) and 12 mutant isolates (6.70%). The proportions of wild-type P. falciparum isolates were 95.72% (134/140), 79.25% (126/159) and 95.83% (161/168) in the target amplification fragments of the three regions in the Pfap2mu gene (Pfap2mu-inner1, Pfap2mu-inner2, Pfap2mu-inner3), respectively. There were 16 different SNPs identified in all successfully sequenced P. falciparum isolates, in which 7 non-synonymous mutations were detected, including S160N, K199T, A475V, S508G, I511M, L595F, and Y603H. There were 7 out of 43 Pfap2mu-mutant P. falciparum isolates (16.28%) that harbored only one gene mutation site, in which non-synonymous mutations accounted for 28.57% (2/7). For the known delayed clearance locus S160N associated with ACTs, there were 143 wild-type (89.94%) and 16 Pfap2mu-mutant P. falciparum isolates (10.06%). CONCLUSIONS: Both Pfubp1 and Pfap2mu gene mutations were detected in P. falciparum isolates from Bioko Island, Equatorial Guinea from 2018 to 2020, with a low prevalence rate of Pfubp1 gene mutation and a high prevalence rate of Pfap2mu gene mutation. In addition, new mutation sites were identified in the Pfubp1 (E1504E and K1520E) and Pfap2mu genes (A475V and S508G).

Marburg Virus Outbreak in Equatorial Guinea: Need for Speed.

The co-existence of deadly viral pandemics can be considered a nightmare for public health authorities. The surge of a Marburg virus disease (MVD) outbreak in Africa at a time when the coronavirus-19 (COVID-19) pandemic is partially controlled with its limited resources is an urgent call for concern. Over the past decades, several bouts of MVD outbreaks have occurred in Africa with an alarming case fatality rate. Despite this, little has been done to end its recurrence, and affected countries essentially depend on preventative rather than curative measures of management. The recent outbreak of MVD declared by the health officials of Equatorial Guinea, causing several deaths in the context of the COVID-19 pandemic, signals the need for speed in the establishment and the implementation of appropriate health policies and health system strategies to contain, destroy, and prevent the spread of this deadly virus to other neighboring countries.

Assessing IRS performance in a gender-integrated vector control programme on Bioko Island, Equatorial Guinea, 2010-2021.

BACKGROUND: Indoor residual spraying (IRS) is a common vector control strategy in countries with high malaria burden. Historically, social norms have prevented women from working in IRS programmes. The Bioko Island Malaria Elimination Project has actively sought to reduce gender inequality in malaria control operations for many years by promoting women's participation in IRS. METHODS: This study investigated the progress of female engagement and compared spray productivity by gender from 2010 to 2021, using inferential tests and multivariable regression. Spray productivity was measured by rooms sprayed by spray operator per day (RSOD), houses sprayed by spray operator per day (HSOD), and the daily productivity ratio (DPR), defined as the ratio of RSOD to HSOD, which standardized productivity by house size. RESULTS: The percentage of women participating in IRS has increased over time. The difference in DPR comparing male and female spray operators was only statistically significant (p < 0.05) for two rounds, where the value was higher for women compared to men. Regression analyses showed marginal, significant differences in DPR between men and women, but beta coefficients were extremely small and thus not indicative of a measurable effect of gender on operational performance. CONCLUSIONS: The quantitative analyses of spray productivity are counter to stigmatizing beliefs that women are less capable than male counterparts during IRS spray rounds. The findings from this research support the participation of women in IRS campaigns, and a renewed effort to implement equitable policies and practices that intentionally engage women in vector control activities.

Rural-Urban Inequities in Tuberculosis-Related Practices in Equatorial Guinea.

BACKGROUND: Tuberculosis (TB) is one of the leading causes of mortality from a single infectious disease agent. Equatorial Guinea is a country with high estimated TB incidence in 2021 (275 cases per 100,000 population) and low TB case detection (42%). Early diagnosis and prompt treatment are crucial for TB control. Failure to seek adequate health care increases the disease's transmission and leads to poor treatment outcome, the mortality, even for easily manageable conditions. Information regarding community management of TB and treatment-seeking patterns in Equatorial Guinea is rare. The aim of this study was to explore differences in TB health-seeking behaviour among urban and rural population TB cases in Equatorial Guinea and the factors associated with this behaviour. METHODS: A national cross-sectional study of 770 household caregivers was conducted in 2020 in Equatorial Guinea using multistage stratified sampling. The 284 caregivers that reported having had a TB case in their family were included in this study. A practice index was created. Poisson regression with robust variance was performed with the practices index as dependent variable to assess the factors associated with the health-seeking behaviour. RESULTS: Most of the cases (65%) have had good TB health-seeking practices. However, 23.2% of TB cases reported having abandoned treatment before 6 months. A higher probability of having good TB practices was observed with being women, aged and living in rural area. Those who were TB cases themselves have heard about TB on the radio, and had high knowledge about TB, hand also good practices. CONCLUSIONS: Disparities in tuberculosis health-seeking behaviour between rural and urban populations highlight the challenges existing in the fight against this infectious disease. The National Tuberculosis Control Program has to reinforce the health system needs to strengthen the follow-up of TB patients taking into account the population at risk of inappropriate TB behaviour. TRIAL REGISTRATION: Not applicable.

Update on the Phylodynamic and Genetic Variability of Marburg Virus.

The COVID-19 pandemic has not only strained healthcare systems in Africa but has also intensified the impact of emerging and re-emerging diseases. Specifically in Equatorial Guinea, mirroring the situation in other African countries, unique zoonotic outbreaks have occurred during this challenging period. One notable resurgence is Marburg virus disease (MVD), which has further burdened the already fragile healthcare system. The re-emergence of the Marburg virus amid the COVID-19 pandemic is believed to stem from a probable zoonotic spill-over, although the precise transmission routes remain uncertain. Given the gravity of the situation, addressing the existing challenges is paramount. Though the genome sequences from the current outbreak were not available for this study, we analyzed all the available whole genome sequences of this re-emerging pathogen to advocate for a shift towards active surveillance. This is essential to ensure the successful containment of any potential Marburg virus outbreak in Equatorial Guinea and the wider African context. This study, which presents an update on the phylodynamics and the genetic variability of MARV, further confirmed the existence of at least two distinct patterns of viral spread. One pattern demonstrates a slower but continuous and recurring virus circulation, while the other exhibits a faster yet limited and episodic spread. These results highlight the critical need to strengthen genomic surveillance in the region to effectively curb the pathogen's dissemination. Moreover, the study emphasizes the importance of prompt alert management, comprehensive case investigation and analysis, contact tracing, and active case searching. These steps are vital to support the healthcare system's response to this emerging health crisis. By implementing these strategies, we can better arm ourselves against the challenges posed by the resurgence of the Marburg virus and other infectious diseases.

First-ever Marburg virus disease outbreak in Equatorial Guinea and Tanzania: An imminent crisis in West and East Africa.

The Marburg virus, which is a member of the same virus family as the Ebola virus called Filoviridae, causes the severe infectious disease known as Marburg virus disease (MVD). Previously, different outbreaks of MVD have appeared in different African countries, including Ghana, Guinea, Uganda, Angola, the Democratic Republic of the Congo, Kenya, and South Africa. For the first time, Equatorial Guinea and Tanzania are experiencing MVD outbreaks. A total of 17 laboratory-confirmed cases of MVD and 23 probable cases have been reported in Equatorial Guinea since the confirmation of the outbreak on February 13, 2023. The first MVD outbreak in the United Republic of Tanzania was formally confirmed by the Ministry of Health on March 21, 2023. As of 22 March, there were eight cases and five fatalities (case fatality ratio [CFR]: 62.5%). Due to the facts that Ebebiyin and Nsock Nsomo districts, the affected regions of Equatorial Guinea, borders Cameroon and Gabon, and Kagera region, the affected region of Tanzania, borders Uganda, Rwanda, and Burundi, there is fear of cross-border spread of MVD due to cross-border migrations, and this can be a great crisis in West and East Africa. Although there are currently outbreaks of MVD in Equatorial Guinea and Tanzania, there is currently no proof of an epidemiological connection between the two outbreaks. The aim of this article is to describe MVD, describe its first outbreak in Equatorial Guinea and Tanzania, explain the efforts being used and the challenges being faced in MVD mitigation, and recommend different measures to be taken to cope with the outbreak of MVD in Equatorial Guinea and Tanzania.

Spatial ecology and conservation of leatherback turtles (Dermochelys coriacea) nesting in Bioko, Equatorial Guinea.

Bioko Island (Equatorial Guinea) hosts important nesting habitat for leatherback sea turtles, with the main nesting beaches found on the island's southern end. Nest monitoring and protection have been ongoing for more than two decades, although distribution and habitat range at sea remains to be determined. This study uses satellite telemetry to describe the movements of female leatherback turtles (n = 10) during and following the breeding season, tracking them to presumed offshore foraging habitats in the south Atlantic Ocean. Leatherback turtles spent 100% of their time during the breeding period within the Exclusive Economic Zone (EEZ) of Equatorial Guinea, with a core distribution focused on the south of Bioko Island extending up to 10 km from the coast. During this period, turtles spent less than 10% of time within the existing protected area. Extending the border of this area by 3 km offshore would lead to a greater than threefold increase in coverage of turtle distribution (29.8 ± 19.0% of time), while an expansion to 15 km offshore would provide spatial coverage for more than 50% of tracking time. Post-nesting movements traversed the territorial waters of Sao Tome and Principe (6.4%of tracking time), Brazil (0.85%), Ascension (1.8%), and Saint Helena (0.75%). The majority (70%) of tracking time was spent in areas beyond national jurisdiction (i.e. the High Seas). This study reveals that conservation benefits could be achieved by expanding existing protected areas stretching from the Bioko coastal zone, and suggests shared migratory routes and foraging space between the Bioko population and other leatherback turtle rookeries in this region.

The SPIN framework to control and prevent the Marburg virus disease outbreak in Equatorial Guinea.

A full grasp of the epidemiological factors promoting transmission is necessary for responding to highly infectious diseases, which involves their control and prevention. With the recent outbreak of Marburg Virus Disease (MVD) in Equatorial Guinea, we saw the need to re-shed some technical light based on our field experiences and published literature. We reviewed 15 previous MVD outbreaks globally. Coupled with core One-Health approaches, we highlighted the SPIN (socio-environmental context, possible transmission routes, informing and guiding public health action, needs in terms of control measures) framework as a guiding tool for response teams to appropriately approach this highly contagious infectious disease outbreak for collective and stronger global health security. The Central African Regional Collaborating Centre (RCC) of the Africa Centres for Disease Control and Prevention (Africa CDC) has a big lead role to play, most especially in coordinating the community engagement and risk communication packages of the response, which is highly needed at this point. We reiterate that this framework remains relevant, if not timely, in rethinking pandemic preparedness and response in resource-limited settings.

Prevalence, intensity and associated risk factors of soil-transmitted helminth infections among individuals living in Bata district, Equatorial Guinea.

BACKGROUND: Soil transmitted Helminths (STH) infections remain a public health concern worldwide, particularly in tropical and subtropical areas where these diseases are highly endemic. Knowing the prevalence and risk factors of the disease is crucial for efficient STH control strategies in endemic areas. The scarcity of epidemiological data on STH for Equatorial Guinea has motivated the decision to perform the present study. METHODS: A cluster-based cross-sectional study was carried out in Bata district from November 2020 to January 2021. Stool samples were collected for the diagnostic of STH infections using Kato-Katz technique. Descriptive statistics was performed for determination of STH prevalence and intensity, while logistic regression models were used to assess the risk factors associated with STH infections. RESULTS: A total of 340 participants were included in the study with a mean age of 24 years (SD = 23.7) and 1.2 female-to-male sex-ratio. The overall prevalence of any STH was 60% (95%CI: 55-65). The most prevalent species were Ascaris lumbricoides (43%, 95%CI: 37-48) and Trichuris trichiura (40%, 95%CI: 35-46). Intensity of infection were mainly light to moderate. A trend of association was observed between age and any STH infection (overall p-value = 0.07), with a significant difference observed between children aged 5-14 years as compared to those aged 1-4 (aOR 2.12; 95%CI: 1.02-4.43, p-value = 0.04), while locality was significantly associated with STH infection (overall p-value<0.001) with a higher odds observed for peri-urban area as compared to urban area (aOR 4.57; 95%CI: 2.27-9.60, p-value<0.001). CONCLUSION: Bata district is a high STH transmission area, where school-aged children and peri-urban areas are associated with a higher risk of any STH infection. This situation calls for a full implementation of the WHO recommendations for STH control; mass drug administration of anthelminthic twice a year to the whole population with great attention to school age children, and prioritizing peri-urban areas where safe water, improve sanitation, and hygiene education should be implemented to achieve a better control.

Safety and Immunogenicity of Radiation-Attenuated PfSPZ Vaccine in Equatoguinean Infants, Children, and Adults.

The radiation-attenuated Plasmodium falciparum sporozoites (PfSPZ) Vaccine has demonstrated safety and immunogenicity in 5-month-old to 50-year-old Africans in multiple trials. Except for one, each trial has restricted enrollment to either infants and children or adults < 50 years old. This trial was conducted in Equatorial Guinea and assessed the safety, tolerability, and immunogenicity of three direct venous inoculations of 1.8 × 106 or 2.7 × 106 PfSPZ, of PfSPZ Vaccine, or normal saline administered at 8-week intervals in a randomized, double-blind, placebo-controlled trial stratified by age (6-11 months and 1-5, 6-10, 11-17, 18-35, and 36-61 years). All doses were successfully administered. In all, 192/207 injections (93%) in those aged 6-61 years were rated as causing no or mild pain. There were no significant differences in solicited adverse events (AEs) between vaccinees and controls in any age group (P ≥ 0.17). There were no significant differences between vaccinees and controls with respect to the rates or severity of unsolicited AEs or laboratory abnormalities. Development of antibodies to P. falciparum circumsporozoite protein occurred in 67/69 vaccinees (97%) and 0/15 controls. Median antibody levels were highest in infants and 1-5-year-olds and declined progressively with age. Antibody responses in children were greater than in adults protected against controlled human malaria infection. Robust immunogenicity, combined with a benign AE profile, indicates children are an ideal target for immunization with PfSPZ Vaccine.