Exploring interrelationships between structural, social, and biological determinants of vaccine impact in Kenya and Uganda: VAnguard community mixed methods study protocol

<ns3:p>Background The key principle underlying the UN Sustainable Development Goals is to “leave no one behind”. However, following the COVID-19 pandemic, sub-optimal vaccine coverage is a continuing concern in low-and middle-income countries (LMICs) and there is increasing evidence of impaired vaccine immunogenicity and efficacy in LMICs, compared to high-income countries (HICS) and in rural, compared to urban settings. It is documented that countries with the lowest vaccination coverage suffer the highest health inequalities. For vaccines to achieve their full health benefit, structural, social and biological determinants that impair vaccine impact must be concurrently addressed. This study aims to explore how structural, social and biological determinants interact to influence vaccine impact in vulnerable communities across Kenya and Uganda. By understanding these interactions, we can develop strategies to improve vaccine impact in vulnerable populations. Methods The study will utilise a cross-sectional mixed-methods design. It will be conducted in three counties in Kenya (Kilifi, Kwale and Kisumu) and three districts in Uganda (Kampala, Kikuube and Namayingo). We will conduct (i) in-depth interviews, (ii) focus group discussions (FGDs) with key community stakeholders, and (iii) a household-based quantitative survey where blood and stool samples of 1032 participants (172 in each community) will be collected. Samples will be used to measure proxy markers of reduced vaccine coverage and impaired vaccine immunogenicity. Conclusions The results of this study will identify potential determinants of vaccine impact that are modifiable. This evidence will be used in the development of a modelling framework to assess the likely impact of interventions targeting specific determinants of impact, both solely and concertedly, and how these might be tailored to different communities.</ns3:p>