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Background: In November 2010, Sierra Leone distributed over three million long-lasting insecticide-treated nets (LLINs) with the objective of providing protection from malaria to individuals in all households in the country. Methods: We conducted a nationally representative survey six months after the mass distribution campaign to evaluate its impact on household insecticide-treated net (ITN) ownership and use. We examined factors associated with household ITN possession and use with logistic regression models. Results: The survey included 4,620 households with equal representation in each of the 14 districts. Six months after the campaign, 87.6% of households own at least one ITN, which represents an increase of 137% over the most recent estimate of 37% in 2008. Thirty-six percent of households possess at least one ITN per two household members; rural households were more likely than urban households to have ≥1:2 ITN to household members, but there was no difference by socio-economic status or household head education. Among individuals in households possessing ≥1 ITN, 76.5% slept under an ITN the night preceding the survey. Individuals in households where the household head had heard malaria messaging, had correct knowledge of malaria transmission, and where at least one ITN was hanging, were more likely to have slept under an ITN. Conclusions: The mass distribution campaign was effective at achieving high coverage levels across the population, notably so among rural households where the malaria burden is higher. These important gains in equitable access to malaria prevention will need to be maintained to produce long-term reductions in the malaria burden. © 2012 Bennett et al.
Sierra Leone is located in West Africa and is bounded by Guinea to the North and East, Liberia to the South, and the Atlantic Ocean to the South and West. The population was 4.9 million at the time of the 2004 Census [12] and was projected to be roughly 5.7 million people by 2010, with an estimated 17.7% of the population being children under the age of 5 years and 5% being pregnant women [13]. Malaria is endemic, with stable and perennial transmission in all parts of the country. The rainy season typically lasts from May to October, with peak rainfall in July and August. Malaria is the leading cause of morbidity and mortality in Sierra Leone, accounting for roughly half of all health system outpatient visits and 38% of hospital admissions, and contributing an estimated 38% and 25% to under-five and all-age mortality rates, respectively [14]. The percentage of households owning at least one ITN was mostly recently estimated (in 2008) to be 37% percent [13]. The LLIN campaign was conducted in all districts of Sierra Leone as part of a one-week National Integrated Maternal and Child Health Campaign from November 25th to December 2nd, 2010 that included house-to-house administration of vitamin A, oral polio vaccine, and albendazole to children under five. Vaccination and distribution teams were selected by District Health Management Teams (DHMTs) and their respective communities; training of team members and supervisors was conducted at national, district, and zonal levels the week preceding the campaign. LLIN vouchers were distributed during house-to-house registration visits for pick-up at distribution points in the community, and distribution points remained open for the entire week. The number of LLINs allocated according to household size was as follows: 1–2 persons: 1 LLIN; 3–4 persons: 2 LLINs; 5 or more persons: 3 LLINs. In addition to household visits, knowledge of the LLIN distribution and education campaigns was communicated through community and religious gatherings and a one-day Health Fair in all communities at the start of the week. Community volunteers were trained from December 10th to 16th, 2010 to help household members properly hang their nets for sleeping. Volunteers conducted household visits, and a revisit if the household was away, to demonstrate and promote proper net hanging and use. Hammers, string and nails were provided to physically assist households with the hanging of nets. The post-campaign survey was conducted in all districts of Sierra Leone from June 20 to June 30, 2011. A two-stage cluster sampling design with primary sampling units (PSUs) selected with probability relative to their size (PPS) was used to ascertain a probability sample within survey domains consisting of all districts of Sierra Leone. The sampling frame was based on population estimates from the National Population and Housing Census [12]. The sample size was based on producing a relatively precise estimate for the proportion of households possessing at least one ITN within each of the 14 survey domains, represented by the 14 administrative districts of Sierra Leone. It was estimated that a sample size of 325 households per survey domain was needed to obtain estimates within each domain with a maximum tolerable error of +/− 6% (absolute percentage points), assuming a design effect of 1.5, a probability of committing a type-1 error of 5% (2-tailed test), an initial population proportion of ITN household coverage of 75 percent, and a non-response rate of 10%. To achieve this, 30 PSUs were randomly selected per domain proportional to their size (PPS), with 11 households selected within each PSU. In total, 4,620 households were sampled from 420 clusters in 14 survey domains. Field teams were trained in the use of personalized digital assistants (PDAs) equipped with GPS for enumerating households in each enumeration area, selecting households, and navigating to selected households for interview. In enumeration areas with an estimated household size of less than 200, all households were enumerated with the PDA, and 11 households were randomly selected for interview. In enumeration areas with an estimated household size of equal to or more than 200, field teams segmented the enumeration area into four equally sized sectors with the help of enumeration area maps and local guides. One segment was then randomly selected for complete enumeration. After complete enumeration of that segment, 11 households were randomly selected for interview. In some cases PDAs become non-operational in the field. To save time in these cases, field teams enumerated households with chalk and selected the 11 households for interview with random number tables. The questionnaire was adapted from a template recommended for use by the RBM MERG Task Force on Household Surveys, and was consistent with those used in the DHS and MIS. The questionnaire collected information to measure LLIN/ITN ownership, hanging and use and was comprised of introductory questions, household wealth questions, mosquito bed net questions, and malaria knowledge, attitudes, and practices questions. Mosquito net ownership was established by respondent self-report, but interviewers made every effort to visually verify the number and status of nets in the household, and carried photographs of the most common nets available in the country. The research protocol and consent procedure was reviewed and approved by the Ethics Committee of the Sierra Leone Ministry of Health and Sanitation prior to commencement of data collection. Based upon a low literacy rate in the population, verbal informed consent was obtained from all household participants prior to administering the questionnaire, and was recorded on the first page of the questionnaire. Interviewers explained the general purpose, benefits, and any risks of the survey to each respondent in his or her local language, and respondents had the right to refuse participation in the survey at any point. Five primary outcomes were used in this analysis: 1) the proportion of households possessing ≥1 ITN (household level); 2) the proportion of households with ≥1 ITN per 2 household occupants (household level); 3) the proportion of households with ≥1 ITN hanging over a sleeping space (household level); 4) the proportion of household with an ITN used by anyone in the house the previous night (household level); and 5) the proportion of individuals who used an ITN the previous night, within households possessing ≥1 ITN (individual level). A net was defined as an ITN if it was either an LLIN, a pre-treated ITN less than one year old, or had been treated with insecticide within the past 12 months. The possession of ≥1 ITN has been shown to be an excellent indicator of household protection against malaria [1]. Ownership of at least 1 ITN per 2 household residents was established as a measure of intra-household access to ITNs (dichotomized as either having this ratio or not), as ascertained by the net and household rosters. A household was defined as the location where a single-family unit shares meals, and included its usual members and any visitors who stayed in the house the previous night. ITN use by anyone in the house the previous night (dichotomized as either yes or no) was used as a proxy for regular use in the house, which is important to ensure ITNs result in an overall reduction in the vector density in the community [15]–[17]. ITN use was defined as individual use by a household resident the night before the survey, as ascertained by the net and household rosters. Household socioeconomic status was based on a principal components analysis (PCA) of household assets [18], including household characteristics such as water source, floor type, sanitation facilities, electricity, and ownership of durable goods such as a television and a refrigerator. In a manner similar to previous work assessing equity in ITN coverage [11], we incorporated differences in wealth between rural and urban areas by first splitting the rural sample into five quintiles, weighted by household size, based upon household asset scores calculated from the first component from the PCA. The same cutoffs were then applied to urban households to create the national index. Investigation of descriptive statistics and bivariate associations between the primary outcomes and hypothesized explanatory variables was first done to guide statistical analyses and subsequent model building. Bivariate associations between outcomes and individual, household and community characteristics were first tested using a Rao-Scott Chi-square test to account for correlated data within primary sampling units. Associations between outcomes and explanatory variables were assessed within logistic regression models while adjusting for potential confounders. Results are presented as adjusted odds ratios. All analyses were weighted to account for discrepancies between the PSU size in the sampling frame and the actual PSU size found in the field during household enumeration. The Taylor Series Linearization approach was used to obtain empirically estimated standard errors for all point estimates and regression coefficients to account for correlated data within primary sampling units. All logistic regression models included district to control for unobservable community-level factors. All analyses were conducted in SAS 9.1 [19]. Figures were created in Stata 10.0 [20] and ArcGIS 9.3 [21]. Based on the characteristics of the National Integrated Maternal and Child Health Campaign that provided mass, free distribution of ITNs to all households in the country, the ‘hang-up’ campaign that followed, and previous research [22], [23], the following household characteristics were hypothesized to be associated with ITN household possession (measured by possession of ≥1 ITN and having ≥1 ITN per 2 household residents): urban/rural status, household wealth (in quintiles measured from the asset index), knowing that mosquitoes transmit malaria (by household head), knowledge that ITNs are effective at preventing malaria (by household head), household head reporting having heard a message on malaria in the past 12 months, the number of people in the household (dichotomized as ≤5 and >5), the number of sleeping spaces in the household (dichotomized as ≤3 and >3), having a child <5 years old in the household, and having a woman of reproductive age (15–49 years) in the household. Due to collinearity between household size, having a child <5 years old, and having a woman of reproductive age, household size was omitted from the model predicting possession of ≥1 ITN, and having a child <5 years old and having a woman of reproductive age were omitted from the model predicting ≥1 ITN per 2 household residents. Factors hypothesized to be associated with the proportion of households with ≥1 ITN hanging over a sleeping space, which is a primary determinant of it being used [10], [23], included urban/rural status, household wealth (in quintiles measured from the asset index), knowing that mosquitoes transmit malaria (by household head), knowledge that ITNs are effective at preventing malaria (by household head), household head reporting having heard a message on malaria in the past 12 months, having ≥1 ITN per 2 household residents, reported misuse of an ITN, and whether someone came to hang up a net in the house in the past year. Based on the mass-free distribution campaign, the national “hang-up” campaign that followed, and previous research [10], [23]–[28] factors hypothesized to be associated with individual ITN use the previous night included the following: urban/rural status, household wealth (in quintiles measured from the asset index), knowing that mosquitoes transmit malaria (by household head), knowledge that ITNs are effective at preventing malaria (by household head), household head reporting having heard a message on malaria in the past 12 months, having ≥1 ITN per 2 household residents, reported misuse of an ITN, whether someone came to hang up a net in the house in the past year, and the individual's age and sex.
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