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Published on: May 30, 2019
Malaria hospitalisation in East Africa: age, phenotype and transmission intensity
Alice Kamau1, Robert S Paton2, Samuel Akech3
1Kenya Medical Research Institute (KEMRI) - Wellcome Trust Research Programme, Nairobi, Kenya. akamau@kemri-wellcome.org.
Insights
Malaria hospitalizations are most common in young children, especially in high transmission areas. Targeting interventions like vaccines to regions with parasite prevalence over 10% aligns with disease burden and intervention age groups.
Area of Science:
- Epidemiology
- Infectious Diseases
- Global Health
Background:
- Understanding age-specific disease patterns is crucial for effective and cost-efficient public health interventions.
- New malaria control strategies, including chemoprevention and vaccines, are increasingly targeting young children through routine immunization services.
- This study investigates the interplay between age, malaria severity, and malaria transmission intensity.
Purpose of the Study:
- To analyze the relationship between age and malaria hospitalization severity in relation to malaria transmission intensity.
- To inform the optimal targeting of malaria chemoprevention and vaccination programs based on age and transmission levels.
- To identify age groups most affected by malaria across different transmission settings.
Main Methods:
- A review of clinical data from 21 surveillance hospitals in East Africa.
- Analysis of malaria admissions in children aged 1 month to 14 years from 2006 onwards.
- Matching hospital data with model-estimated community-based age-corrected parasite prevalence (PfPR2-10) to assess transmission intensity.
Main Results:
- Over 52,000 malaria admissions were analyzed across varying transmission intensities (PfPR2-10 <1% to 48.7%).
- The majority of malaria hospitalizations (69-85%) occurred in children under 5 years old, with significantly fewer cases in older children (10-14 years).
- Mean age of hospitalization was lower in high transmission settings (34.1 months) compared to low transmission (49.5 months), with similar trends for severe malaria phenotypes like cerebral malaria (CM).
Conclusions:
- Targeting malaria chemoprevention and vaccination programs to areas with community parasite prevalence of 10% or higher is recommended.
- This strategy aligns intervention age ranges (e.g., 2-23 months) with the age groups experiencing the highest burden of malaria and severe disease.
- Optimizing intervention delivery based on age and transmission intensity can maximize cost-effectiveness and impact.
Background:
Understanding the age patterns of disease is necessary to target interventions to maximise cost-effective impact. New malaria chemoprevention and vaccine initiatives target young children attending routine immunisation services. Here we explore the relationships between age and severity of malaria hospitalisation versus malaria transmission intensity.
Methods:
Clinical data from 21 surveillance hospitals in East Africa were reviewed. Malaria admissions aged 1 month to 14 years from discrete administrative areas since 2006 were identified. Each site-time period was matched to a model estimated community-based age-corrected parasite prevalence to provide predictions of prevalence in childhood (PfPR2-10). Admission with all-cause malaria, severe malaria anaemia (SMA), respiratory distress (RD) and cerebral malaria (CM) were analysed as means and predicted probabilities from Bayesian generalised mixed models.
Results:
52,684 malaria admissions aged 1 month to 14 years were described at 21 hospitals from 49 site-time locations where PfPR2-10 varied from < 1 to 48.7%. Twelve site-time periods were described as low transmission (PfPR2-10 < 5%), five low-moderate transmission (PfPR2-10 5-9%), 20 moderate transmission (PfPR2-10 10-29%) and 12 high transmission (PfPR2-10 ≥ 30%). The majority of malaria admissions were below 5 years of age (69-85%) and rare among children aged 10-14 years (0.7-5.4%) across all transmission settings. The mean age of all-cause malaria hospitalisation was 49.5 months (95% CI 45.1, 55.4) under low transmission compared with 34.1 months (95% CI 30.4, 38.3) at high transmission, with similar trends for each severe malaria phenotype. CM presented among older children at a mean of 48.7 months compared with 39.0 months and 33.7 months for SMA and RD, respectively. In moderate and high transmission settings, 34% and 42% of the children were aged between 2 and 23 months and so within the age range targeted by chemoprevention or vaccines.
Conclusions:
Targeting chemoprevention or vaccination programmes to areas where community-based parasite prevalence is ≥10% is likely to match the age ranges covered by interventions (e.g. intermittent presumptive treatment in infancy to children aged 2-23 months and current vaccine age eligibility and duration of efficacy) and the age ranges of highest disease burden.
