Adolescent Acceptance of Diphtheria Booster Dose in Kano, Nigeria: A Cross-Sectional Mixed-Methods Study.

BACKGROUND: Diphtheria remains a vaccine-preventable disease of public health concern in low- and middle-income countries, with recurrent outbreaks linked to immunity gaps among older children and adolescents. In Nigeria, although routine infant immunisation coverage has improved, uptake of recommended booster doses among adolescents remains suboptimal. This study assessed factors associated with acceptance of the diphtheria booster dose among in-school adolescents in Kano metropolis, northern Nigeria. METHODOLOGY: A cross-sectional explanatory sequential mixed-methods study was conducted among 650 adolescents aged 10-19 years. Quantitative data were collected using a structured questionnaire and analysed with descriptive statistics, chi-square tests, and logistic regression. Qualitative data were obtained through focus group discussions and key informant interviews with adolescents, parents, and teachers, and analysed thematically to contextualise quantitative findings. RESULTS: Overall, 81.8% of respondents expressed willingness to accept the diphtheria booster dose. In adjusted analysis, acceptance was significantly associated with being in senior secondary school (aOR = 2.21; 95% CI: 1.31-3.75). Parental marital status (aOR = 0.56; 95% CI: 0.34-0.91), parental education (aOR = 0.58; 95% CI: 0.35-0.94), and knowledge of the booster dose (aOR = 0.20; 95% CI: 0.10-0.41) were also significantly associated with acceptance. Qualitative findings revealed that willingness was often conditional on parental approval, perceived vaccine safety, and service availability. Key barriers included poor awareness, misconceptions, fear of side effects, and limited parental involvement, while facilitators included school-based health education, peer influence, parental encouragement, teacher support, and school-based vaccination platforms. CONCLUSION: Although stated willingness to accept the diphtheria booster dose was high, acceptance is influenced by school-related, parental, and perceptual factors. Strengthening school-based vaccination platforms, enhancing parental engagement, and implementing culturally sensitive communication strategies may improve booster uptake and prevent future outbreaks.