Exploring the Landscape of Routine Immunization in Nigeria: A Scoping Review of Barriers and Facilitators

"Tailored approaches that consider the socio-economic, cultural, and logistical challenges specific to each region are essential to bridge the immunization gap."

According to the United Nations Children's Fund (UNICEF) and the World Health Organization (WHO), Nigeria holds a large share of burden of zero-dose and under-immunised children, with an estimated over 2.1 million based on 2023 estimates. Furthermore, there are significant regional inequalities that are exacerbated by parental hesitancy and resistance, primarily fuelled by rumours about vaccine safety and reinforced by religious and cultural considerations. This scoping review systematically maps and summarises existing literature on the barriers and facilitators of immunisation in Nigeria, focusing on regional inequalities.

A search of electronic databases was conducted, encompassing all data from their inception to October 2023, to identify articles on the determinants of routine immunisation uptake in Nigeria. Vaccines studied included: Bacillus Calmette-Guérin (BCG) vaccine; diphtheria, tetanus, and pertussis (DTP)-containing vaccine; polio vaccines; and measles-containing vaccines (MCV). Overall, 110 studies were included and used for evidence synthesis and mapping. The scoping review presents results of data involving a combined 271,273 participants, comprising caregivers, community influencers, and immunisation implementing stakeholders.

Key facilitators of routine immunisation in Nigeria include:
 

• Caregiver-related drivers: Of all the factors identified in various studies, maternal education of at least secondary education or higher was the most frequently mentioned. Across all studies, cultural and religious factors emerged prominently, alongside positive social support. Trust in healthcare providers, maternal discretion in vaccination decision-making without husband's consent, being married or maintaining a monogamous family structure, and the provision of incentives such as free transportation to vaccination services were also identified as also playing significant roles in driving immunisation uptake.
• Health-system-related drivers: Adequate vaccine supply, presence of a skilled healthcare workforce, and timely immunisation reminder systems and strong health information systems played were identified as key elements of health-system related drivers. 
• Community/social context-related drivers: Community leader influence, community engagement, and social mobilisation emerged as noteworthy drivers. The presence of vaccine advocates in the community and putting adequate security protection in place via engagement of security personnel were also reported.

Overall, the long distance between caregivers' homes and immunisation centres stands out as the most frequently reported impediment to routine immunisation uptake. Other identified barriers include:
 

• Caregiver-related barriers: The fear of side effects of immunisation and misinformation emerged as prominent concerns. In addition, cultural or religious beliefs and lack of awareness about the immunisation schedule were key factors shaping caregivers' perceptions and behaviours.
• Health-system-related barriers: Vaccine shortages emerged as the most prominent issue; poor interpersonal communication between healthcare workers and caregivers further hinders effective immunisation delivery.
• Community/social context-related barriers: Residency in rural or urban slum areas was key, as was ethnicity, with authors reporting high vaccine hesitancy or refusal among Hausa/Fulani ethnic groups compared to Yoruba and Igbos and cultural or religious beliefs playing substantial roles. Challenges from insurgency, conflict, and insecurity, along with high vaccine hesitancy or refusal among internally displaced individuals and migrants, were also noted. Distrust in the healthcare system, female-headed households, low literacy rates in communities, and lack of social support were additional barriers impacting childhood immunisation.

The results revealed unique regional differences:
 

• In the North-East, significant factors included peer influence, robust reminder systems, provision of additional security, and financial incentives for health facilities.
• In the North-West, perceived vaccine benefits, fear of non-immunisation consequences, urban residence, health literacy, and antenatal care visits were reported as crucial.
• In the North-Central zone, perceived benefits of vaccines and trust in healthcare providers were identified as predominant factors.
• In the South-East, maternal autonomy, health literacy, and fear of non-immunisation consequences were important.
• In the South-South, peer influence and reminder systems like WhatsApp and short messaging service (SMS) were notable, alongside higher maternal education levels.
• The South-West highlighted maternal autonomy, peer influence, health card usage, high maternal education, and supportive government policies as critical factors.

Based on the findings, some overall recommendations to address barriers to improve immunisation coverage across Nigeria include:
 

• Direct efforts toward fostering community engagement, building trust, and conducting tailored awareness campaigns within religious communities to dispel myths, address concerns, and promote the importance of immunisation for overall community health.
• In light of misinformation, take proactive measures to dispel myths and allay fears regarding immunisation to foster trust and encourage higher vaccination rates.
• Empower women financially and specifically engage males during immunisation mobilisation to address the fact that the reviewed studies frequently cited instances of male heads of households refusing immunisation.
• Deploy dedicated teams of female vaccinators and female community influencers to bolster acceptance and accessibility.
• Take cultural festivities and rites info consideration when planning immunisation campaigns to ensure maximum participation and accessibility for caregivers.
• Develop comprehensive solutions to health-system-related barriers, spanning from targeted training programmes to alleviate communication gaps among healthcare providers to strategic workforce planning initiatives aimed at mitigating staffing shortages.
• Gain insights into caregivers' schedules via community feedback and adopt flexible immunisation campaign strategies to improve accessibility by aligning immunisation schedules with caregivers' routines.
• Prioritise hard-to-reach conflict-affected regions during outreach campaigns, and put in place heightened security measures to safeguard routine immunisation personnel and give confidence to the populace.

The paper underscores the need for region-specific interventions, noting that, in addressing the challenges of immunisation across Nigeria's six geopolitical zones, several targeted interventions are recommended based on the distinct socio-cultural and logistical contexts of each region. To cite one example: In the North-West and North-East, where vaccine hesitancy is exacerbated by strong cultural and religious influences, engaging community influencers such as religious and traditional leaders can be a pivotal strategy. These figures, who hold significant sway over public opinion, can effectively advocate for immunisation, thereby counteracting misinformation and fostering trust in healthcare providers.

According to the researchers, "Addressing these challenges requires a multi-faceted approach and strong collaboration among stakeholders and communities." A concerted effort will be made to address the factors identified in the study in line with the mandate of the Gavi-led Zero-Dose Learning Hub, which is implemented by the AFENET/AHBN consortium.

Full list of authors, with institutional affiliations: Yahaya Mohammed, African Field Epidemiology Network (AFENET) Nigeria, and Usmanu Danfodiyo University; Heidi W. Reynolds, Gavi, The Vaccine Alliance; Hyelshilni Waziri, AFENET Nigeria; Adam Attahiru, AFENET Nigeria; Ahmed Olowo-okere, Usmanu Danfodiyo University; Moreen Kamateeka, AFENET Nigeria; Ndadilnasiya Endie Waziri, AFENET Nigeria; Aminu Magashi Garba, Africa Health Budget Network (AHBN); Gustavo C. Corrêa, Gavi, The Vaccine Alliance, and Ministry of Health, Kano State, Nigeria; Rufai Garba, National Primary Health Care Development Agency, Abuja, Nigeria; Nancy Vollmer, JSI Research & Training Institute, Inc. (JSI); Patrick Nguku, AFENET Nigeria