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Seasonal Malaria Chemoprevention (SMC)

Seasonal malaria chemoprophylaxis targets children ages 3 months to five years old living in malaria endemic areas with highly seasonal transmission. Complete treatment courses of antimalarial drugs are given to healthy children at monthly intervals during the transmission season, over a maximum of four months. SMC is recommended in areas where the transmission is high and seasonal and where the drugs, sulfadoxine-pyrimethamine (SP) and amodiaquine (AQ) remain highly efficacious. Seasonal treatment reduces parasitaemia among children by maintaining therapeutic drug concentrations in their blood throughout the period of greatest malaria risk. This has the dual effect of preventing malaria illness for these children and lowering the force of transmission in the population. Our model accounts for the protective effect of SMC on the health of the participating children and the broader impact through reduced malaria infections in the community.

PSI distributes pre-packaged treatment courses with recommended doses, based on age. For children ages 3-11 months, a treatment course includes 3 tablets of 76.5 mg of AQ, to be given daily for 3 days, and a 250/12.5 mg SP tablet, to be given on the first day. For a children ages 12-59 months, a treatment course includes 3 tablets of 153 mg of AQ, to be given daily for 3 days, and a 500/25 mg SP tablet, to be given on the first day. Treatment should be repeated monthly, up to four times, throughout the transmission season.

Unit of intervention
4 pre-packaged treatment courses of SMC

Formulation
Infants ages 3-11 months:
Sulfadoxine-Pyrimethamine (SP) (250/12.5 mg)
Amodiaquine (AQ) (76.5 mg)

Children ages 12-59 months:
Sulfadoxine-Pyrimethamine (SP) (500/25 mg)
Amodiaquine (AQ) (153 mg)

Dosage
SMC requires up to 4 treatment courses at monthly intervals:
1 tablet AQ daily for 3 days and 1 tablet SP on the first day

Target population
Healthy children ages 3-59 months living in areas where >60% of malaria cases occur over a period of a few months, where the clinical rate of malaria is at least 0.1 attack per transmission season in the target age group, and where SP and AQ retain at least 90% efficacy. Children who have an acute febrile illness, are HIV-positive and receiving co-trimoxazole, have received a dose of SP or AQ in the last month, or are allergic to SP or AQ are excluded from the target population.

For more information about how PSI is fighting malaria to improve health and save lives, visit our website at:
http://www.psi.org/health-area/malaria/

Model Overview

PSI’s SMC impact model is based on Avenir Health's malaria module within the Spectrum suite of models. The Spectrum malaria module estimates the impact on all mortality of administration of at least three months of SMC in a single malaria season per child. PSI endeavors to provide four months of treatment to children. We track drug distribution rather than require programs to report children receiving treatment. The output from our model is deaths and DALYs per child receiving 4 pre-packaged treatment courses of SMC.

Model Outputs (impact metrics)

Estimates of DALYs averted and deaths averted represent the projected health impact of the intervention, not the directly measured impact.

Examples based on SMC in Mali 2017 Statement of modeled results, examples:

If 10,000 children receive 4 pre-packaged treatment courses in Mali during the 2017 rainy season, an estimated 36 deaths and 3,130 DALYs would be averted.

For more details about how PSI models the impact of SMC, see below.

Model Details

Step 1: Running a projection in Spectrum

PSI starts by running a projection in Spectrum for Sahel countries. In these projections, SMC coverage is scaled up from country baseline to 90%. Spectrum then projects the number of all-age deaths averted by this increased level of SMC coverage. For more information on Spectrum’s malaria modules, consult the following paper published in Malaria Journal: Korenromp 2017 and Hamilton 2017.

Spectrum models all mortality reduction based on a child receiving 3 of 4 monthly treatments where as the PSI intervention assumes 4 monthly treatments. So as not to over attribute health impact from the PSI intervention, the PSI model calculates impact based on a child receiving the recommended full treatment course of 4 pre-packaged treatment courses.

Step 1 Output:
Number of additional all-age deaths averted (or lives saved) by increasing SMC coverage from current country levels to 90%.

Step 2: Estimating all-age deaths averted per child receiving SMC

PSI takes the output from step 1 (deaths averted at 90% coverage of SMC) to estimate the number of all-age deaths averted by one child receiving 4 pre-packaged treatment courses. This is done by dividing the number of deaths averted at 90% by the number of children that need to receive 4 pre-packaged treatment courses to reach 90% SMC coverage.

PSI estimates the number of children who would need to receive 4 pre-packaged treatment courses to reach 90% coverage using parameters like population size of children under five years of age, wastage and a county’s baseline SMC coverage.

Step 2 Output:
Deaths averted coefficient for SMC

Step 3: Estimating all-age DALYs averted per child receiving SMC

A DALY (or disability adjusted life year) includes two components: years of life lost due to premature death (YLL) and years lived with disability (YLD). DALYs averted is the sum of YLL and YLDs averted. At PSI, we calculate the number of DALYs averted as a result of our interventions.

To estimate YLL averted per child receiving 4 pre-packaged treatment courses, PSI first estimates the number of years of life lost per malaria death in each country. This is equal to the life expectancy at average age of death for malaria. The number of years of life lost per malaria death is then multiplied by the number of deaths averted per child who received 4 pre-packaged treatment courses calculated in step 2 above. This gives us the YLL averted per child who received 4 pre-packaged treatment courses.

To estimate YLDs averted per child who received 4 pre-packaged treatment courses, we use the country-specific YLD/YLL ratio, based on GBD 2015 data. This ratio represents the relative number of years lived with disability for every year lost due to malaria death. We apply this ratio to the number of YLL averted per child receiving 4 pre-packaged treatment courses to estimate the number of YLD averted per child receiving SMC. YLL and YLD averted are added together to get the estimated number of DALYs averted per child receiving 4 pre-packaged treatment courses.

Step 3 Output:
DALYs averted coefficient for SMC