The association between travel time to health facilities and childhood vaccine coverage in rural Ethiopia. A community based cross sectional study

Background: Few studies have examined associations between access to health care and childhood vaccine coverage in remote communities that lack motorised transport. This study assessed whether travel time to health facilities was associated with childhood vaccine coverage in a remote area of Ethiopia. Methods: This was a cross-sectional study using data from 775 children aged 1259 months who participated in a household survey between January July 2010 in Dabat district, north-western Ethiopia. 208 households were randomly selected from each kebele. All children in a household were eligible for inclusion if they were aged between 1259 months at the time of data collection. Travel time to vaccine providers was collected using a geographical information system (GIS). The primary outcome was the percentage of children in the study population who were vaccinated with the third infant Pentavalent vaccine ([Diphtheria, Tetanus,-Pertussis Hepatitis B, Haemophilus influenza type b] Penta3) in the five years before the survey. We also assessed effects on BCG, Penta1, Penta2 and Measles vaccines. Analysis was conducted using Poisson regression models with robust standard error estimation and the Wald test. Results: Missing vaccination data ranged from 4.6% (36/775) for BCG to 16.4% (127/775) for Penta3 vaccine. In children with complete vaccination records, BCG vaccine had the highest coverage (97.3% [719/739]), Penta3 coverage was (92.9% [602/648]) and Measles vaccine had the lowest coverage (81.7% [564/690]). Children living ?60mins from a health post were significantly less likely (adjRR = 0.85 [0.79-0.92] p value≤0.001) to receive Penta3 vaccine compared to children living <30mins from a health post. This effect was not modified by household wealth (p value = 0.240). Travel time also had a highly significant association with BCG (adjRR = 0.95 [0.93-0.98] p value =0.002) and Measles (adjRR = 0.88 [0.79-0.97] p value =0.027) vaccine coverage. Conclusions: Travel time to vaccine providers in health posts appeared to be a barrier to the delivery of infant vaccines in this remote Ethiopian community. New vaccine delivery strategies are needed for the hardest to reach children in the African region. © 2012 Okwaraji et al.

The study was implemented in the Dabat Health and Demographic Surveillance Site (HDSS) in Dabat district, north-western Ethiopia. The HDSS consists of three urban and seven rural kebeles – the smallest administrative unit in Ethiopia. The population in the HDSS is currently 46,165 and is dominated by the Amhara ethnic group [8]. A typical house has walls constructed from mud and wood. Livestock are commonly kept in the house and the economy is mainly based on subsistence farming and trading. There are few roads in this part of Ethiopia. Off-road motorised transport is not viable in most areas because of the difficult terrain. The main form of travel is walking and the mountainous region and poor road network means that families spend many hours walking to farms, health facilities and administrative centres. The under five mortality rate in Dabat district has recently been reported as 130 per 1,000 live births [9]. The vaccine schedule in Dabat district comprises: Bacille Calmette Guérin (BCG); Pentavalent vaccine (Diphtheria, Tetanus, Pertussis, Hepatitis B and Haemophilus influenzae type b vaccines combined in one syringe) at 6 weeks (Penta 1), 10 weeks (Penta2) and 14 weeks (Penta3); oral polio vaccine (OPV) at 6 weeks (Polio1), 10 weeks (Polio2) and 14 weeks (Polio3) and measles vaccine at 9 months. There are a total of 8 rural health posts in Dabat district (one kebele has two health posts and all other rural kebeles have one health post). In Dabat district, vaccines are mostly administered in the health posts. Health posts are the lowest level of health care and staffed by two female health extension workers recruited from the community and trained for one year to provide a range of essential health interventions including childhood immunisation for the rural population [10]. Vaccines are provided approximately once a month to all children attending the health post [3]. Due to limited time and staffing the health extension workers do not perform home visits to provide vaccines. There are no refrigerators to keep the vaccines in the health posts and they are brought in a vaccine carrier from Dabat health centre on the scheduled date for immunisation and left over vaccines are taken back to the health centre the same day. The other source of vaccine delivery in the study area is the national immunisation days. These are currently used for Polio and Measles vaccines and are implemented by national immunisation staff in community locations (e.g. village market places, schools, churches or mosques) as well as the health posts. This was a cross-sectional study conducted in the seven rural kebeles of the HDSS between January and July 2010. 208 households were randomly selected from a list of the rural kebele households supplied by the HDSS using a computer generated sequence. Children were eligible for inclusion if they were aged between 12–59 months at the time of data collection. Trained data collectors visited households and identified eligible children who were present at the time of the survey. Information recorded during the interview included: demographic characteristics of mothers, household asset information needed for the construction of wealth terciles, the place of the child’s birth and whether delivery was assisted by skilled birth attendants. After obtaining informed written consent from the child’s mother, the data collectors asked the mothers questions and entered the responses directly into the hand-held computers (PDAs). Vaccination data for five vaccines (BCG, Penta1, Penta2, Penta3 and Measles) were recorded from the vaccine card obtained from the mother at the beginning of the interview. If there was no card, data were obtained from the mother, based on her memory about the vaccination. Immunisation data were double checked from the health post vaccination register book and information was added or corrected where needed. Polio vaccination data were not recorded as both maternal recall and health post registration for these vaccines was very poor. Methods for calculation of the measures of geographical access are detailed elsewhere [9]. In brief, travel time was calculated using the “Cost analysis” module in the IDRISI Taiga Geographic Information System (GIS) software package. The module requires two input layers of data. The first layer contains the target location (the health posts), and the second layer contains the costs (in terms of the time spent walking) associated with moving through different geographical features in the study area to reach the target feature. Different features (e.g. walking up hills and mountains and traversing through water) are assigned different speeds. The output from the module is an image where each cell (pixel) in the image contains values of travel time required to traverse from that cell to the health post. In this study, a speed of 5 km/hr was assigned for all walking routes, slopes greater than 30 degrees were assigned a speed of 0.1 km/hr and traversing through water bodies was also assigned a speed of 0.1 km/hr. Travel time for each household was extracted and exported into Stata to merge with the main dataset. Validation of the model was described in detail in our previous paper [9]. In brief, reported travel time from 40 village centre were obtained and compared with estimated travel time. Mean reported and estimated travel times were very close (mean, 73 vs. 67 minutes; standard deviation, 46 vs. 40 minutes, respectively). All analyses were performed in Stata SE 12.0 (StataCorp LP, College Station, TX 77845, USA). Travel time was examined as a categorical variable divided into terciles (<30mins, 30- < 60mins and ≥60 mins) and as a continuous variable (based on the number of minutes of travel time from the household to the health post). The primary outcome variable was the percentage of children aged 12–59 months who received Penta3 vaccine at any time before the survey was conducted. This vaccine was chosen as it is most commonly used by international groups such as WHO and UNICEF [11]. To estimate the wealth status of each household, we constructed a relative asset index based on data collected on housing material and household assets. The index was constructed using principal component analysis (PCA). Children in the sample were ranked in order of the asset index values for their households, and then they were divided into one of three equal sized terciles, ranking from the least poor to the poorest. In the univariable analyses, we first assessed associations between Penta3 coverage, travel time, household wealth and potential confounding variables such as: demographic characteristics of mothers (age group, education level, and parity). In the multivariable analysis we investigated the relationship between the probability of receiving Penta3 vaccine and travel time to health posts using Poisson regression models with robust standard error estimation. We first accounted for the intra cluster correlation of many children from the same mother, many mothers from the same village and many villages from the same kebele. However, there was only evidence of within kebele clustering of vaccination coverage and no evidence of clustering at the village or mother level. Thus, the final model only adjusted for clustering at the kebele level. The model also included confounding variables which had p value of <0.1 for their association with travel time to health posts and vaccine coverage. We also examined statistical interactions between travel time and household wealth status and hypothesised a priori that the effect of travel time on vaccine coverage might be different in rich and poor women. The Wald test was used to compare the fit of models containing different variables, to test for trend in ordered categorical variables and to test for a statistical interaction between travel time and household wealth. These analyses were repeated for the four other vaccines (BCG, Penta1, Penta2 and Measles). The most recent Ethiopian Demographic and Health Survey (DHS) reported 32% of children aged 12–59 months are immunised with Penta3 vaccine by age 12 months [12]. The Dabat HDSS reported that there were approximately 600 children aged 12–59 months in the study area. We calculated that these children would provide 80% power at a 5% significance level to detect at least a 10% difference in Penta3 vaccination coverage between children who lived < 60 minutes from a health post compared to those who lived ≥ 60 minutes. This study was approved by the ethical review committees of the University of Gondar and the London School of Hygiene and Tropical Medicine. Verbal informed consent to conduct interviews was received from all heads of participating households. Written informed consent to participate in the study was obtained from mothers of all children who were included in the study.

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