Genetic Diversity and Protective Efficacy of the RTS,S/AS01 Malaria Vaccine.

BACKGROUND: The RTS,S/AS01 vaccine targets the circumsporozoite protein of Plasmodium falciparum and has partial protective efficacy against clinical and severe malaria disease in infants and children. We investigated whether the vaccine efficacy was specific to certain parasite genotypes at the circumsporozoite protein locus. METHODS: We used polymerase chain reaction-based next-generation sequencing of DNA extracted from samples from 4985 participants to survey circumsporozoite protein polymorphisms. We evaluated the effect that polymorphic positions and haplotypic regions within the circumsporozoite protein had on vaccine efficacy against first episodes of clinical malaria within 1 year after vaccination. RESULTS: In the per-protocol group of 4577 RTS,S/AS01-vaccinated participants and 2335 control-vaccinated participants who were 5 to 17 months of age, the 1-year cumulative vaccine efficacy was 50.3% (95% confidence interval [CI], 34.6 to 62.3) against clinical malaria in which parasites matched the vaccine in the entire circumsporozoite protein C-terminal (139 infections), as compared with 33.4% (95% CI, 29.3 to 37.2) against mismatched malaria (1951 infections) (P=0.04 for differential vaccine efficacy). The vaccine efficacy based on the hazard ratio was 62.7% (95% CI, 51.6 to 71.3) against matched infections versus 54.2% (95% CI, 49.9 to 58.1) against mismatched infections (P=0.06). In the group of infants 6 to 12 weeks of age, there was no evidence of differential allele-specific vaccine efficacy. CONCLUSIONS: These results suggest that among children 5 to 17 months of age, the RTS,S vaccine has greater activity against malaria parasites with the matched circumsporozoite protein allele than against mismatched malaria. The overall vaccine efficacy in this age category will depend on the proportion of matched alleles in the local parasite population; in this trial, less than 10% of parasites had matched alleles. (Funded by the National Institutes of Health and others.).

Are tropical mangroves a sink for litter leaking from land-and sea-based sources? Evidence from selected Kenyan mangroves.

Marine litter surveys were carried out to determine the role of mangroves as a sink for litter. General litter density in the mangroves was 0.088 ± 0.076 items m-2, composed mainly of plastic (85.9 %). Higher litter densities occurred in the middle (0.162 ± 0.150 items m-2) compared to the landward (0.066 ± 0.049 items m-2) and the seaward zones (0.036 ± 0.028 items m-2), indicating the important role played by the middle zone in providing a sink for litter from both land and sea-based sources. Landward zones were a sink for heavier litter from land that could easily be trapped by mangrove roots (plastic and clothing). The middle zones retained mainly the litter that are not easily trapped by the mangroves' roots in seaward and landward zones, particularly soft plastics. The seaward zones acted as a sink for litter from sea-based sources mainly marine and fishing gears, and materials used for fishing and boat repairs.

In-vivo efficacy of amodiaquine-artesunate in children with uncomplicated Plasmodium falciparum malaria in western Kenya.

OBJECTIVES: To assess the efficacy of amodiaquine-artesunate in an area with high chloroquine resistance in western Kenya. METHODS: Twenty-eight day in-vivo efficacy trial of amodiaquine-artesunate in 103 children aged 6-59 months in western Kenya with smear-confirmed uncomplicated Plasmodium falciparum malaria. RESULTS: The 28-day uncorrected adequate clinical and parasitological response (ACPR) was 69.0%, with 15.5% Late Clinical Failure and 15.5% Late Parasitologic Failure rates. The PCR-corrected 28-day ACPR was 90.2%. Clinical risk factors for recurrent infection (recrudescences and reinfections) were lower axillary temperature at enrollment and low weight-for-age Z-score. The presence of single nucleotide polymorphisms pfcrt 76T and pfmdr1 86Y at baseline was associated with increased risk of recurrent infections, both reinfections and recrudescences. CONCLUSION: Although artemether-lumefantrine (Coartem) is the first line ACT in Kenya, amodiaquine-artesunate is registered as an option for treatment of uncomplicated P. falciparum and remains an effective alternative to Coartem in western Kenya. Continued amodiaquine monotherapy in the private sector may jeopardize the future use of amodiaquine-artesunate as an alternative artemisinin-based combination therapy.

Commonly cited incentives in the community implementation of the emergency maternal and newborn care study in western Kenya.

BACKGROUND: Mortality of mothers and newborns is an important public health problem in low-income countries. In the rural setting, implementation of community based education and mobilization are strategies that have sought to reduce these mortalities. Frequently such approaches rely on volunteers within each community. OBJECTIVE: To assess the perceptions of the community volunteers in rural Kenya as they implemented the EmONC program and to identify the incentives that could result in their sustained engagement in the project. METHOD: A community-based cross sectional survey was administered to all volunteers involved in the study. Data were collected using a self-administered supervision tool from all the 881 volunteers. RESULTS: 881 surveys were completed. 769 respondents requested some form of incentive; 200 (26%) were for monetary allowance, 149 (19.4%) were for a bicycle to be used for transportation, 119 (15.5%) were for uniforms for identification, 88 (11.4%) were for provision of training materials, 81(10.5%) were for training in Home based Life Saving Skills (HBLSS), 57(7.4%) were for provision of first AID kits, and 39(5%) were for provision of training more facilitators, 36(4.7%) were for provision of free medication. CONCLUSION: Monetary allowances, improved transportation and some sort of identification are the main incentives cited by the respondents in this context.