Abstract
BACKGROUND: The measles vaccine represents one of the most efficacious means of safeguarding pediatric populations against the measles virus. Empirical evidence consistently demonstrates that over 99% of recipients who complete the two-dose regimen achieve immunity to the disease. Despite this high efficacy, suboptimal vaccine coverage persists as a significant impediment to the containment and eventual eradication of measles. To augment immunization coverage, routine vaccination programs are often supplemented by second-dose opportunities administered through Supplemental Immunization Activities (SIAs), particularly in countries with a high measles burden. This study aims to evaluate the measles vaccination coverage attained after the nationwide SIAs in May 2025 as well as vaccination coverage prior to SIAs. METHODS: This study was conducted from May 26th to June 5th, 2025. A two-stage cluster sampling design was utilized, where 938 clusters were randomly selected from a national sampling frame of 6,936. This sampling frame covered all accessible districts, villages, and nomadic areas throughout the country. The sample size was calculated using the WHO-2018 manual, resulting in the selection of 134 clusters and 1,780 households from each state, culminating in 12,832 interviews overall. A total of 355 interviewers, equipped with the KoboCollect app for digital data collection, conducted surveys. We calculated vaccine coverage during supplemental immunization activities (SIAs) and prior to SIAs (which means routine immunization). To calculate the national coverage, a survey weighting methodology was applied. Specific procedures were used to determine cluster and household weights, following the formula outlined in the WHO Vaccination Coverage Cluster Survey 2018. Both descriptive and inferential statistics were applied. Descriptive statistics, including frequency counts and proportions, enabled us to summarize the general attributes of the sample. Conversely, inferential statistics were used to estimate national vaccine coverage, featuring point estimates and confidence intervals (Wilson 95% Confidence Intervals), with the application of survey weights. Ethical approval was obtained from the Somali National University Ethical Committee. RESULTS: Of 17,700 children across seven states, 46.5% were girls and 53.5% were boys. Most children (56.2%) lived in urban areas, followed by 25.8% in rural areas and 14.2% in nomadic areas. Additionally, 3.76% of children lived in Internally Displaced Persons (IDP) camps. Weighted coverage estimates indicate that 73% (CI: 68.14-77.3) of children in Somalia received the measles vaccine during SIAs. Regarding the regional variation of vaccine coverage, the highest coverage was observed in Somaliland (87.4%, CI: 81,7-91.3) and Puntland (87.1%, CI: 82.7-90.5), while the lowest were found in Hirshabelle (48%, CI: 32.6-63.8) and Southwest (50%, CI: 40.4-59.7) states. In terms of geographic settlements, the nomadic population had the lowest measles vaccine coverage during SIAs (70.9%, CI: 57.8-81.3), and had the highest zero-dose children of 15.4% (CI: 8.9-25.2) compared to urban and rural populations. The national measles coverage prior to SIA was found to be 78,6% (CI: 74.6-82.09). The SIAs achieved a national coverage rate of 39.8% among children who had previously received no doses (zero-dose children) and 82% among those who had received at least one dose prior. The predominant reason for children not being vaccinated during the SIAs was a lack of awareness about the vaccination campaign. DISCUSSION: The lowest national vaccine coverage and the highest proportion of zero-dose children were predominantly found in the Hirshabelle and Southwest states and among nomadic communities. This difference in vaccine coverage among states and communities is concerning and suggests the need for targeted intervention to address these gaps.