title: Insecticide-treated net effectiveness at preventing Plasmodium falciparum infection varies by age and season.
abstract: After increasing coverage of malaria interventions, malaria prevalence remains high in Malawi. Previous studies focus on the impact of malaria interventions among children under 5 years old. However, in Malawi, the prevalence of infection is highest in school-aged children (SAC), ages 5 to 15 years. This study examined the interaction between age group and insecticide-treated net (ITN) use for preventing individual and community-level infection in Malawi.
  
  
  
  Six cross-sectional surveys were conducted in the rainy and dry seasons in southern Malawi from 2012 to 2014. Data were collected on household ITN usage and demographics. Blood samples for detection of Plasmodium falciparum infection were obtained from all household members present and over 6 months of age. Generalized linear mixed models were used to account for clustering at the household and community level.
  
  
  
  There were 17,538 observations from six surveys. The association between ITN use and infection varied by season in SAC, but not in other age groups. The adjusted odds ratio (OR) for infection comparing ITN users to non-users among SAC in the rainy season and dry season was 0.78 (95% CI 0.56, 1.10) and 0.51 (0.35, 0.74), respectively. The effect of ITN use did not differ between children under five and adults. Among all non-SACs the OR for infection was 0.78 (0.64, 0.95) in those who used ITNs compared to those that did not. Community net use did not protect against infection.
  
  
  
  Protection against infection with ITN use varies by age group and season. Individual estimates of protection are moderate and a community-level effect was not detected. Additional interventions to decrease malaria prevalence are needed in Malawi.
authors.affiliation: Institute for Global Health, University of Maryland School of Medicine, 685W, Baltimore St. HSF-1 Room 480, Baltimore, MD, 21201, USA.
authors.forename: Andrea G
authors.initials: AG
authors.lastname: Buchwald
authors.affiliation: University of Michigan School of Public Health, 1415 Washington Heights, Ann Arbor, MI, 48109, USA.
authors.forename: Jenna E
authors.initials: JE
authors.lastname: Coalson
authors.affiliation: Institute for Global Health, University of Maryland School of Medicine, 685W, Baltimore St. HSF-1 Room 480, Baltimore, MD, 21201, USA.
authors.forename: Lauren M
authors.initials: LM
authors.lastname: Cohee
authors.affiliation: Institute for Global Health, University of Maryland School of Medicine, 685W, Baltimore St. HSF-1 Room 480, Baltimore, MD, 21201, USA.
authors.forename: Jenny A
authors.initials: JA
authors.lastname: Walldorf
authors.affiliation: University of Malawi College of Medicine, Chichiri, Private Bag 360, Blantyre, Malawi.
authors.forename: Nelson
authors.initials: N
authors.lastname: Chimbiya
authors.affiliation: University of Malawi College of Medicine, Chichiri, Private Bag 360, Blantyre, Malawi.
authors.forename: Andy
authors.initials: A
authors.lastname: Bauleni
authors.affiliation: University of Malawi College of Medicine, Chichiri, Private Bag 360, Blantyre, Malawi.
authors.forename: Kondwani
authors.initials: K
authors.lastname: Nkanaunena
authors.affiliation: University of Malawi College of Medicine, Chichiri, Private Bag 360, Blantyre, Malawi.
authors.forename: Andrew
authors.initials: A
authors.lastname: Ngwira
authors.affiliation: Institute for Global Health, University of Maryland School of Medicine, 685W, Baltimore St. HSF-1 Room 480, Baltimore, MD, 21201, USA.
authors.forename: John D
authors.initials: JD
authors.lastname: Sorkin
authors.affiliation: University of Malawi College of Medicine, Chichiri, Private Bag 360, Blantyre, Malawi.
authors.forename: Don P
authors.initials: DP
authors.lastname: Mathanga
authors.affiliation: Department of Osteopathic Medicine, Michigan State University, West Fee Hall, 909 Fee Road, Room B305, East Lansing, MI, 48824, USA.
authors.forename: Terrie E
authors.initials: TE
authors.lastname: Taylor
authors.affiliation: Institute for Global Health, University of Maryland School of Medicine, 685W, Baltimore St. HSF-1 Room 480, Baltimore, MD, 21201, USA. mlaufer@medicine.umaryland.edu.
authors.forename: Miriam K
authors.initials: MK
authors.lastname: Laufer
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D018562:Disease Transmission, Infectious / Q000517:prevention & control*; D005260:Female; D006302:Health Services Research; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D057148:Insecticide-Treated Bednets / Q000706:statistics & numerical data*; D016778:Malaria, Falciparum / Q000517:prevention & control*; D008295:Malawi; D008297:Male; D008875:Middle Aged; D009032:Mosquito Control / Q000379:methods*; D012621:Seasons; D055815:Young Adult
keywords: Insecticide-treated nets; Malawi; Plasmodium falciparum; School-aged children; Universal distribution campaign