ITNs have been shown to reduce morbidity and mortality, but coverage continues to be moderate in many parts of sub-Saharan Africa. As much of the malaria control community is shifting away from a narrow strategy of targeted ITN use amongst vulnerable groups such as children <5 years old and pregnant women and towards universal coverage, we explored the gains made through a routine health facility-based distribution system and the potential steps needed to achieve universal coverage. Through the use of health facility-based distribution, Malawi has been able to achieve moderate household ITN possession (59%) and use by all persons (49%), but is still short of universal coverage. However, this distribution strategy is hampered by various factors. First, only 67% of eligible households received an ITN through health facility-based distribution, thus suggesting that this system can only reach a portion of the target population. Although ANC and vaccination clinic attendance is high with 96% of women aged 15–49 years who completed a pregnancy in the past two years attended ANC at least once during their last pregnancy and 97% of children receiving at least one vaccination by 12 months of age 
, this distribution system is still not reaching all eligible pregnant women and children. The efficiency of this system needs to be improved (e.g. decreased ITN stockouts, all women presenting to ANC receiving an ITN) to improve its impact. Second, only 72% of households have a pregnant women or a child <5 years old, thus not all households can be reached by this strategy. However, we found that 36% of households that were ineligible for health facility-based distribution had an ITN obtained from a health facility. This suggests that despite efforts to target ITN distribution, there is a re-distribution of ITNs to the entire population. As countries move towards universal ITN coverage, health facility-based distribution might be an effective means to keep up household ITN possession in between campaigns and might be moderately successful in even reaching ineligible households.
However, despite the moderate success of health facility-based distribution, this strategy is unlikely to lead to universal coverage. We explored the inputs needed (number of ITNs) and the expected coverage achieved by different distribution strategies. Our analysis suggests that universal coverage campaigns that target all households will lead to better distribution of ITNs between households than targeted campaigns that distribute ITNs either to children <5 years old or children 5–15 years old. In addition, a universal coverage campaign to distribute 2 ITNs per household or 1 ITN per sleeping space will require similar inputs and achieve similar coverage. Given the potential difficulty of defining a sleeping space during a distribution campaign, it is likely that a campaign that distributes 2 ITNs per household might be logistically less challenging. A campaign that distributes 1 ITN per 2 people would provide the highest coverage, but would require the largest inputs.
Despite moderate levels of household ITN possession, ITN use among persons who resided in a household with an ITN was high (76%), especially for children <5 years old and pregnant women. Over 92% of all ITNs in the households were hanging at the time of the survey and each net was used by a mean of 2.4 persons, suggesting that concerns that ITNs are not being used are unfounded in this case. Our multivariate logistic regression model suggests that among persons who resided in a household with at least one ITN, use was associated with being in a target group for facility-based free distribution and the number of ITNs per household. Use among all persons increased with increasing number of ITNs per household suggesting that a key barrier to higher ITN use amongst all household members is the lack of ITNs in the household.
Our analysis of ITN possession and use by socioeconomic status suggests two different patterns. Households in the poorer quintiles were less likely to own ITNs despite free distribution through health facilities. This pattern suggests that there might be barriers to persons from poorer households in obtaining ITNs. These barriers might be reduced access to health facilities due to either distance or cost, residing in areas in which health facilities offer poor quality services and have a less functional ITN distribution system, or reduced knowledge about the health facility-based ITN distribution program. However, persons residing in the poorer households were more likely to use the ITNs if they owned them. As children who reside in poorer households have greater disease burden (parasitemia and anemia) than children in less poor households, the potential gains on both reducing inequities in ITN possession as well as disease burden might be substantial if we adopted distribution strategies that are likely to be equitable. Prior equity analyses of ITN distribution campaigns suggest that these campaigns (either universal or targeted) can reduce inequities in ITN possession 
more quickly and effectively than other strategies.
Although almost all of Malawi experiences malaria transmission, there are marked district level differences in both disease burden and ITN possession and use. The health facility-based ITN distribution program is national, but we noted district-level differences in coverage with ITNs obtained from health facilities. These district level differences might be due to differences in population (e.g. socioeconomic status) as well as the functionality of the health system at the district level. In our analysis we adjusted for socioeconomic status differences, but could not account for other confounders (e.g. education level). District-level differences need to be examined further to better understand potential determinants of district-level health system performance as measured by its ability to deliver key preventive interventions such as ITNs. In addition, measuring and understanding district-level differences might be useful for targeting high disease burden, low coverage districts to achieve maximum coverage with scarce resources.
ITNs have been shown to reduce morbidity and mortality in numerous controlled trials 
. In our analysis, use of ITNs and untreated bednets by children <5 years old was associated with reduced asexual parasitemia prevalence, a measure of malaria endemicity, and anemia prevalence, a common manifestation of malaria infection that leads to poor health outcomes in children. Thus, we demonstrate a significant disease-specific impact of ITN use in children <5 years old. Given a population of 1,084,969 children <5 years old of a total population of 4,339,876 in the eight districts based on the 2008 census, current levels of ITN use are associated with an estimated 33,908 fewer children with asymptomatic parasitemia and 36,384 fewer children with anemia, and if universal coverage was achieved with all children sleeping under ITN then we can expect 55,587 fewer children with parasitemia and 59,646 fewer children with anemia. In our analysis, both untreated bednets and ITNs had a similar association with reduced parasitemia and anemia prevalence; this finding needs to be explored further.
As we aim for universal coverage, we need to understand both the distribution of ITNs between households as well as within households. In this analysis from Malawi, we show the impact of a particular ITN distribution strategy on achieving household ownership and how this translates into ITN use by individual household members. An understanding of these dynamics is critical to evaluate current distribution programs as well as design future distribution strategies. These types of analyses as well as reporting of both household ITN possession (already done by most major surveys such as the Malaria Indicator Survey (MIS) and Demographic and Health Surveys (DHS)) as well as ITN use by all household members (not currently done by most major surveys) are critical in monitoring our progress towards universal coverage and identifying gaps in coverage, such as low use by particular age groups (e.g. in Malawi, low use by children 5–15 years old).
This study has a number of limitations. We report a survey from 8 of 28 districts in Malawi. Although, these districts contain 33% of the population of Malawi and are geographically diverse, these districts were purposively selected as sentinel districts and thus our findings are not representative of all of Malawi. As with all survey data, the findings are limited by recall and social desirability biases. However, the recall period for most questions was relatively short (e.g. the previous night) and many aspects of ITN possession (e.g. possession of net and its location in the household) and socioeconomic status (e.g. possession of assets and house construction variables) were confirmed by visual inspection.
Effective vector control through the use of ITNs is one strategy to reduce the substantial malaria burden in Malawi. ANC and vaccination clinic based distribution of ITNs has increased household ITN possession to moderate levels, but falls short of universal coverage. Universal coverage mass distribution campaigns will be needed to achieve maximal public health impact. A successful ‘keep up’ distribution strategy needs to be supplemented with periodic ‘catch up’ campaigns.