Trends and inequalities in full immunisation coverage among one-year-olds in Sierra Leone, 2008-2019.

Background: Full immunisation of children by their first birthday is a crucial public health target. Vaccines protect children from preventable diseases, promoting individual and community health. In Sierra Leone, a country with a history of high childhood mortality rates, achieving full immunisation coverage is a critical step towards a healthier future. This study examined the trends and inequalities in full immunisation coverage among children aged one year in Sierra Leone from 2008 to 2019.

Methods: Three rounds of the Sierra Leone Demographic and Health Survey (2008, 2013, and 2019) were analysed. A descriptive approach was adopted for the analysis. Simple [difference (D) and ratio (R)] and complex [population attributable risk (PAR) and population attributable fraction (PAF)] measures of inequalities were computed using the World Health Organization's Health Equity Assessment Toolkit (WHO's HEAT) software. The measures were computed separately for each of the three surveys, and their estimates were compared.

Results: The findings revealed that full immunisation coverage for one-year-olds in Sierra Leone increased significantly between 2008 (40.1%) and 2013 (68.3%). However, there was a decrease in coverage in 2019 (56.5%). Region-related inequalities were the largest and increased slightly between 2008 (D = 13.8; R = 1.4; PAF = 17.8, PAR = 7.1) and 2013 (D = 20.7.; R = 1.3; PAF = 14.2, PAR = 9.7) but decreased in 2019 (D = 18.2; R = 1.3; PAF = 15.3, PAR = 8.6). Substantial education-related inequalities were observed in 2008 (D = 10.1, R = 1.2, PAF = 19.4, PAR = 7.7), but this decreased in 2013 (D = 6.7, R = 1.1, PAF = 8.0, PAR = 5.4; and 2019 D = 5.0, R = 1.0, PAF = 4.7, PAR = 2.4). The age and sex of the child appeared to have minimal influence on the overall inequality in immunisation coverage.

Conclusion: The study highlights education and region as key contributors to the inequalities. Mothers with lower education were less likely to get their children fully immunised. Immunisation coverage varies significantly across regions, with the Eastern region leading and the Northern region lagging. Age and sex have minimal impact. The government and partner organisations in Sierra Leone should focus outreach programs on these high-risk groups, implement geographically targeted strategies and invest in education and improve access to healthcare facilities. Ensuring vaccine availability, trained personnel, and data collection for monitoring could be useful. There is also the need to develop targeted interventions for regions with lower coverage. These steps are crucial to achieving universal immunisation coverage.

Trial registration: Registration was not necessary since we analysed a secondary dataset.