Geographic and temporal variations in immunization coverage in Nepal: an ecological time-trend analysis

Background: Immunization remains a vital public health intervention in Nepal, yet significant disparities persist. This study evaluates the performance of Nepal's national immunization program by analyzing district-level vaccination coverage and dropout rates from 2009 to 2022 to identify trends and disparities across different routine vaccinations. Methods: This study is a secondary ecological analysis of administrative data, where a search of relevant literature was conducted across public websites and databases to identify published literature related to national immunization coverage in Nepal. Only national reports by the Department of Health Services were identified to contain this information and were included in the content analysis. Those national reports covering 77 districts data were extracted and classified according to immunization performance categories: Category 1 (high coverage ≥ 80%, low dropout < 10%), Category 2 (high coverage, high dropout ≥ 10%), Category 3 (low coverage < 80%, low dropout), and Category 4 (low coverage, high dropout). Descriptive statistics and geographic mapping were presented using only information provided in the published literature. Results: Only 8 districts (10.4%) remained consistently in Category 1 throughout 2009–2022, while 39 districts (50.7%) had median Category 1 status. Eight districts (10.4%) were classified as Category 4 at least once. Category 1 districts peaked between 2012 and 2014 but declined by 2019. Category 4 was most prevalent in 2009. Antigen-specific coverage showed BCG maintained the highest coverage, followed by combined DPT-HepB-Hib3, Polio (3 doses), and measles, with Tetanus Toxoid vaccine (TT2 or TT +) being the lowest throughout the duration. Conclusion: While most districts had a median Category 1 status, consistent high performance was limited to a few districts. The persistence of Category 4 districts, particularly in 2009 and 2019, indicates ongoing challenges. Geographic and temporal variations highlight the need for targeted interventions in underperforming districts to improve coverage and reduce dropout rates.