1.1 Background of the study

Community health workers (CHWs) — lay or paraprofessional workers drawn from the communities they serve — are widely used in low- and middle-income countries to extend the reach of primary health services, including childhood immunization (World Health Organization, 2018). CHW outreach strategies commonly include household visits, defaulter tracing, group education, mobilisation for outreach sessions, and basic service delivery support that links clients to fixed or outreach immunization sessions. In contexts where travel costs, time poverty, or weak facility–community linkages limit access to routine immunization, CHW outreach can reduce practical barriers (convenience) and strengthen caregivers’ confidence through trusted interpersonal counselling (World Health Organization, 2018; Ali et al., 2022).

Urban informal settlements such as Ajegunle face a particular mix of obstacles: high population density, mobile households, precarious livelihoods, and often weak or fragmented primary health service provision. Studies in similar settings show that CHW-led demand-generation, combined with service adaptations (flexible clinic hours, outreach on market days), can increase timely vaccination and reduce zero-dose children when the CHW programme is adequately supported (training, supervision, incentives, supply chain linkages) (Rajshekhar et al., 2023; Gichuki et al., 2024). Furthermore, behavioural and social drivers of vaccination — including caregiver beliefs, social norms and information channels — are especially influential in tight social networks typical of slums; CHWs who are trusted insiders can be effective messengers to correct misinformation and normalise vaccination (World Health Organization, 2022; Larson et al., 2022) However, the evidence also cautions that CHW outreach is not uniformly effective: impact depends on programme design (task mix, workload, supervision), integration with supply-side readiness (consistent vaccine stocks, cold chain, and reliable session scheduling), and the local information ecology. Inadequately supported CHWs may be unable to follow up defaulters reliably, and outreach without concurrent improvements in service quality or supply can frustrate communities and reduce trust (World Health Organization, 2018; Ali et al., 2022). For Ajegunle — a densely populated, informal settlement with complex social networks and varied livelihood patterns — assessing how CHW outreach currently functions and whether it measurably increases routine immunization uptake is therefore essential for programmatic planning.

1.2 Statement of the problem

Despite periodic outreach and the presence of community-level actors in many parts of Lagos, routine immunization gaps persist in some informal settlements. Aggregate urban coverage statistics often conceal intra-city pockets where children remain underimmunized or receive doses late (Ali et al., 2022). Ajegunle’s combination of high population density, seasonal migration, informal employment, and variable access to health facilities suggests that facility-centred strategies alone may not reach all children on time. CHW outreach is commonly proposed as a remedy — but in many settings, programme managers lack locality-specific evidence about (a) the current coverage and intensity of CHW outreach activities, (b) whether outreach is associated with higher timely uptake (and which outreach components matter most), and (c) which service-side bottlenecks (stockouts, irregular session timing) may limit outreach effectiveness (Rajshekhar et al., 2023; World Health Organization, 2022).

Without robust, local evidence on the impact of CHW outreach, managers risk allocating resources to outreach models that are under-resourced or misdesigned — for example, expanding CHW numbers without ensuring supervision or supply reliability, or focusing CHW time on one-off mass mobilisation rather than patient tracking and defaulter follow-up. A focused investigation in Ajegunle that links household immunization outcomes with measured CHW outreach exposure (and with facility readiness) will clarify whether and how CHW outreach improves vaccine uptake, and which programmatic adjustments would produce the best return on investment.

1.3 Aim and Objectives of the Study

Aim: To evaluate the impact of community health worker outreach on routine childhood immunization uptake and timeliness among caregivers of children 0–59 months in Ajegunle community, Ajeromi-Ifelodun LGA, Lagos State.

Specific objectives:

1. To measure routine immunization coverage and timely completion (by vaccine and age) among children 0–59 months in Ajegunle.
2. To describe CHW outreach activities in Ajegunle (frequency of household visits, defaulter tracing, group education, role in outreach sessions) and the proportion of caregivers reporting CHW contact in the last 12 months.
3. To compare immunization outcomes (coverage and timeliness) between children whose caregivers report recent CHW outreach contact and those without such contact, adjusting for socio-demographic confounders.
4. To assess facility-level readiness (vaccine stockouts, session scheduling, cold-chain status, and staff availability) for immunization services serving Ajegunle and examine how facility readiness modifies the association between CHW outreach and immunization uptake.
5. To generate programmatic recommendations on how to optimise CHW outreach (task distribution, supervision, incentives, and integration with facility services) to improve routine immunization in Ajegunle.

1.4 Research Questions

1. What are the current rates of routine immunization coverage and timely completion among children aged 0–59 months in Ajegunle?
2. What CHW outreach activities are being carried out in Ajegunle, and what proportion of caregivers report contact with a CHW in the past year?
3. Is caregiver-reported CHW outreach contact associated with higher odds of a child being fully immunized and vaccinated on time, after adjusting for socio-demographic factors?
4. How does facility-level readiness (stockouts, session regularity, staff) affect the relationship between CHW outreach and immunization outcomes?
5. Which specific outreach functions (household visits, defaulter tracing, mobilisation for fixed outreach sessions) are most strongly associated with improved uptake and timeliness?

1.5 Scope of the Study

This study will be conducted in Ajegunle community, Ajeromi-Ifelodun LGA, Lagos State. It will use a mixed-methods design combining: (a) a cross-sectional household survey of caregivers of children 0–59 months to measure vaccination status (card verification where available), timeliness, socio-demographic factors, and caregiver-reported exposure to CHW outreach; (b) a facility assessment of primary health facilities and outreach services serving Ajegunle (cold-chain readiness, recent stockouts, session schedules, staffing levels); and (c) qualitative interviews with CHWs, facility immunization staff, and community leaders to understand outreach practices, barriers, and feasible programme improvements.

Inclusion criteria for the household survey: caregiver (parent or primary guardian) of a child aged 0–59 months who has resided in Ajegunle for at least six months. The quantitative analysis will estimate associations between CHW outreach exposure and vaccine outcomes using logistic regression and survival/interval methods for timeliness, controlling for confounders (maternal education, household income proxy, parity, and length of residence). The facility assessment will document supply-side constraints that may limit outreach effectiveness. Qualitative interviews will explore CHW training, supervision, workload, incentive structures, and community perceptions of outreach. Ethical approval will be obtained from an appropriate institutional review board and consent obtained from all participants.

References

Ali, H. A., Hartner, A.-M., Echeverria-Londono, S., Roth, J., Li, X., Abbas, K., Portnoy, A., Vynnycky, E., Woodruff, K., Ferguson, N. M., Toor, J., & Gaythorpe, K. A. M. (2022). Vaccine equity in low and middle income countries: A systematic review and meta-analysis. International Journal for Equity in Health, 21, Article 82. https://doi.org/10.1186/s12939-022-01678-5

Gichuki, J., Ngoye, B., & Wafula, F. (2024). “I’ll take them another day”: A qualitative study exploring the socio-behavioural complexities of childhood vaccination in urban poor settlements. PLOS ONE, 19(5), e0303215. https://doi.org/10.1371/journal.pone.0303215

Larson, H. J., Gakidou, E., & Murray, C. J. L. (2022). The vaccine-hesitant moment. The New England Journal of Medicine, 387(1), 58–65. https://doi.org/10.1056/NEJMra2106441

Rajshekhar, N., Pinchoff, J., Boyer, C. B., Barasa, E., Abuya, T., Muluve, E., Mwanga, D., Mbushi, F., & Austrian, K. (2023). Exploring COVID-19 vaccine hesitancy and uptake in Nairobi’s urban informal settlements: An unsupervised machine-learning analysis of a longitudinal prospective cohort study from 2021 to 2022. BMJ Open, 13, e071032. https://doi.org/10.1136/bmjopen-2022-071032

World Health Organization. (2018). WHO guideline on health policy and system support to optimize community health worker programmes. World Health Organization.

World Health Organization. (2022). Behavioural and social drivers of vaccination: Tools and practical guidance for achieving high uptake. World Health Organization.