The survival of children aged 0 to 5 remains a major concern in public health. These young children face ongoing threats from preventable diseases, which account for over two million deaths annually worldwide .1 Vaccination stands out as one of the most effective public health interventions ,2 preventing approximately 2.5 million child deaths each year from diphtheria, tetanus, pertussis (whooping cough), and measles .3
Evaluating the strength of a country’s immunisation programme involves monitoring the rate of zero-dose (ZD) children .4 A ZD child is defined as any child eligible for vaccination who has not received the first dose of the pentavalent vaccine which protects against diphtheria, pertussis, tetanus, hepatitis B, and Haemophilus influenzae type b .5–7 This indicator reflects inadequate access to vaccination services.
Globally, nearly 50% of ZD children are concentrated in three key geographic settings: urban slums, remote communities, and conflict zones .8 In sub-Saharan Africa, an estimated 4.4 million children die each year from diseases that are preventable through vaccination. Low coverage remains a major contributor to the re-emergence of these diseases .9
In 2019, five countries Nigeria, India, Pakistan, Ethiopia, and the Democratic Republic of Congo (DRC) accounted for two-thirds of the world’s ZD children. There are major disparities between and within countries. For example, in the DRC and Ethiopia, ZD children are mostly found in isolated rural regions, while in Nigeria, they are concentrated in areas affected by conflict .8
The DRC, located in the heart of Africa, had an estimated population of 98.3 million in 2016, based on census data collected by the health zones. Around 70% of this population lived in rural areas and 30% in urban areas .10,11 The population is predominantly young: 48% under 15 years of age, 18.9% under 5 years, and approximately 4% younger than 12 months.
In the DRC, ZD children are widespread and represent a serious public health challenge. In some provinces, more than half of children remain unvaccinated. The number of estimated ZD children stands between 767,061 and 775,135, representing around 19% .11,12
In Kinshasa, the capital and largest urban province, the rate of ZD children aged 12 to 23 months was reported at 3% in 2021 .7,11 Within the Mont Ngafula 1 Health Zone (HZ) which comprises both urban and rural areas this rate varies significantly between health areas. Among its 17 health areas, Pumbu reported a pentavalent vaccine coverage of 0% for several consecutive months .13
In 2022, vaccination coverage across the Mont Ngafula 1 HZ was just 13%, with an estimated ZD rate of 87% .13,14 During that same year, the zone experienced outbreaks of several vaccine-preventable diseases (VPDs), including three measles outbreaks (14 reported cases), four cases of acute flaccid paralysis (AFP), and four cases of yellow fever .13
These public health consequences suggest the presence of significant factors hindering child immunisation in the Mont Ngafula 1 HZ, despite government efforts such as the MASHAKO Plan. This national strategy aims to strengthen routine immunisation by increasing the number of vaccination sessions near family residences and enhancing vaccine availability .10
This study seeks to identify the key factors associated with zero-dose status among children in Mont Ngafula 1 HZ.
METHODS
Study design
A mixed-methods study was conducted in Mont Ngafula 1 Health Zone (HZ) from April to July 2024. The quantitative component was a cross-sectional analytical survey, and the qualitative component comprised semi-structured interviews.
Study setting
Mont Ngafula 1 HZ covers 358.92 km² with an estimated population of 378,251 in 2022 (density: 727 inhabitants/km²). The zone comprises 17 health areas (9 rural, 8 urban), one public facility, and 31 private clinics (Figure 1).
Population
The study population included all children aged 12–23 months residing in the selected health areas during the study period.
Sample size determination
Assuming a zero-dose prevalence of 20% (p = 0.20) based on the 2020 ECV survey, the minimum sample size was calculated using the formula:
where Z₁₋ₐ/₂ = 1.96 (α = 0.05), d = 0.05, and design effect (DEFF) = 1.5. This yielded:
Allowing for 10% non-response increased the target sample to 406 participants.
Sampling procedure
A three-stage probability sampling design was used:
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Health Areas: Five of 17 health areas were randomly selected.
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Avenues: Within each selected area, 50% of avenues were randomly sampled using official lists.
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Households: Systematic sampling was applied to residential plots; one eligible child per household was selected by random draw when multiple were present.
Administrative and political approvals were obtained prior to data collection. Fifteen interviewers received a two-day training on study procedures, ethical conduct, and tools. A pilot test was conducted in Mont Ngafula 1 from 8–10 April 2024. Data collection then occurred from 15–25 April 2024.
Data collection and management
Quantitative data: Structured questionnaires were used to collect information on child immunization status and potential determinants, including caregiver demographics, socioeconomic factors, and barriers to vaccination. Data were coded in EpiData 3.1, validated, and exported to SPSS v26.0 for analysis. Tables and graphs were generated in Microsoft Excel.
Qualitative data: Semi-structured interviews were conducted with mothers (of fully vaccinated and zero-dose children), community relays (CORE), and registered nurses (RN). Sessions were audio-recorded and transcribed verbatim. Transcripts were imported into ATLAS.ti v7 for coding based on a priori themes, followed by inductive thematic analysis.
Statistical analysis
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Dependent variable: Zero-dose status.
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Independent variables: Caregiver age, child sex, education level, occupation, marital status, religious affiliation, access barriers, and opportunity costs.
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Descriptive statistics: Frequencies and percentages for categorical variables; mean ± SD for normally distributed continuous variables.
Inferential analyses (logistic regression) were planned to identify factors associated with zero-dose status.
Ethical Considerations
The study was approved by the Ethics Committee of the Kinshasa School of Public Health (ESP/CE/81/2024) and authorized by local health and administrative authorities. Written informed consent was obtained from all participants following explanation of the study objectives, procedures, and confidentiality safeguards. Anonymity was maintained, and data access was restricted to the research team.
RESULTS
Quantitative results
We collected data from 406 participants. The socio-demographic characteristics of the participants are presented in Table 1.
Participant Characteristics The majority of participants were, on average, 28 years old, with most falling within the 25–34 age group. Among these, 48% were mothers of ZD children, while 42% were mothers of vaccinated children.
Educational attainment was high across both groups: 98% of mothers of ZD children and 99.6% of mothers of vaccinated children had received formal education.
Religious affiliation varied between groups. A notable proportion of mothers of ZD children (37%) identified with other churches, whereas 40% of mothers of vaccinated children were affiliated with revival churches.
In terms of marital status, 61% of mothers of ZD children and 62% of mothers of vaccinated children reported living in a union.
Employment data revealed that unpaid work was common. Specifically, 98% of mothers of ZD children and 89% of mothers of vaccinated children were engaged in unpaid occupations.
Child and Respondent Demographics Among the 406 children included in the study, the average age was 16.55 months. A majority of zero-dose (ZD) children were female (54%), whereas 52% of vaccinated children were male.
Children aged between 12 and 17 months represented the largest age group, accounting for 62.5% of ZD children and 62% of vaccinated children. In terms of family structure, mothers with at least one child under the age of five comprised 54% of those with ZD children and 62% of those with vaccinated children.
The vast majority of respondents were the children’s mothers, representing 96% of ZD cases and 94% of vaccinated cases.
Furthermore, residence patterns showed that 71% of ZD children and 62% of vaccinated children lived in rural health zones (Table 2).
Maternal knowledge of vaccination Regarding awareness of vaccination, 88% of mothers of zero-dose (ZD) children reported having heard of vaccines, compared with 99% of mothers of vaccinated children (Table 3).
Furthermore, 63% of mothers of ZD children and 53% of mothers of vaccinated children were familiar with at least one vaccine, most commonly the oral polio vaccine (OPV).
Poliomyelitis was the most frequently recognised vaccine-preventable disease (VPD), with 78% of mothers of ZD children and 57% of mothers of vaccinated children identifying it.
However, knowledge of other vaccines was notably limited: 74% of mothers of ZD children and 61% of mothers of vaccinated children had never heard of the pentavalent vaccine.
Additionally, 58% of mothers of ZD children and 48% of mothers of vaccinated children had received vaccination information through alternative sources.
Perceptions of vaccination costs and time investment among the 406 participants interviewed, the average amount considered acceptable to pay for their child’s vaccination was 1,081.58 Congolese Francs (CDF), equivalent to approximately $0.38 (Table 4).
A majority of mothers of zero-dose (ZD) children (50%) and vaccinated children (83%) found the waiting time at vaccination appointments to be acceptable.
When asked about time lost due to vaccination visits, 47% of mothers of ZD children reported missing out on household chores, whereas 58% of mothers of vaccinated children indicated that they forfeited time for other activities.
Regarding payment perceptions, 55% of mothers of ZD children and 24% of mothers of vaccinated children stated that vaccination services had a cost.
Bivariate analysis revealed several significant associations with vaccination status:
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Respondents who had heard of at least one vaccine, particularly the oral polio vaccine (OPV), were significantly less likely to have zero-dose (ZD) children. The odds ratio was 0.5, indicating a 50% reduction in the risk, with a confidence interval (CI) of 0.264–0.969 (Table 5).
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Mothers or carers who had heard of pertussis were associated with an 83% reduced risk of having ZD children (CI: 0.173–0.644).
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Awareness of hepatitis was also significantly associated, reducing the risk of having ZD children by 57% (CI: 0.203–0.924).
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Having knowledge of at least one vaccine-preventable disease (VPD) corresponded with a 50% reduction in the likelihood of having a ZD child (CI: 0.257–0.978).
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In contrast, mothers or carers who paid for vaccination services were 3.6 times more likely to have ZD children (CI: 2.210–5.888).
Multivariate analysis Further analysis identified the following statistically significant associations:
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Increasing age of mothers/carers was associated with a marginally higher likelihood of having ZD children (CI: 1.005–1.113).
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Mothers/carers aged 15–24 years had three times the risk of having ZD children (CI: 1.247–7.692).
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Religious affiliation showed notable associations :
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Catholic respondents were 2.8 times more likely to have ZD children (CI: 1.498–5.558).
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Protestants were twice as likely (CI: 1.023–4.002).
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Revival church members showed a 2.4-fold risk (CI: 1.407–4.263).
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Employment status was also significant: mothers/carers engaged in paid work were 4.8 times more likely to have ZD children (CI: 1.249–18.818).
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Vaccine awareness was protective; those who had heard about vaccines were 0.4 times more likely to have ZD children (representing a 60% reduction in risk, CI: 0.034–0.611).
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Payment for vaccination services increased risk, with a 2.6-fold likelihood of having ZD children (CI: 1.773–3.840).
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Conversely, mothers/carers willing to pay for vaccination if supported by government efforts were associated with a 70% reduced risk of having ZD children (CI: 0.162–0.903).
Qualitative findings
Group discussions with mothers of ZD children revealed a general awareness of vaccination; however, they unanimously expressed unfamiliarity with the pentavalent vaccine and confirmed their children had not been vaccinated.
The key barriers cited were financial, including:
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Lack of funds to purchase the vaccination card
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Misinformation or discouragement from peers and elders who claimed that payment was required for child vaccination
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Perceptions of Cost and Management of Vaccination Services Concerns regarding the management of post-vaccination events (PVEs) were raised during the interviews. One mother stated that she would only allow her child to be vaccinated once the authorities fully implement a system for managing PVEs.
A small number of registered nurses admitted that vaccination sessions and vaccination cards were not free of charge. They noted that if payment is not made at the time of the appointment, the cost at the next session would be doubled to cover missed sessions.
Mothers and carers of zero-dose (ZD) children reported having to pay for both the vaccination and the vaccination card, yet most were unaware of the exact amount required, despite living near health centres. Their understanding of the card’s cost varied: one respondent mentioned a figure of $25 USD, while others cited 2,000 or 5,000 Congolese Francs (CDF). (Exchange rate at the time of the study: $1 = 2,800 CDF.)
Knowledge barriers
Several mothers of zero-dose (ZD) children expressed doubts regarding the efficacy and safety of vaccines. One mother remarked: “I did not vaccinate my child because I am unsure of the vaccine’s effectiveness. I received all the vaccines as a child, yet I suffered from polio and was hospitalised for over a month. If my children receive these vaccines, can you guarantee they won’t fall ill again—with tetanus, tuberculosis?”
Concerns about side effects were also evident. One mother shared: “My son has never been vaccinated. How many injections will he receive—twelve all at once? He will be in a lot of pain.”
Mothers affiliated with the “Vutuka Vana Mpambu Wavidila” (VUVAMU or Black Church) expressed strong distrust toward vaccines. While they acknowledged being aware of vaccines, they unanimously rejected their use. One explained: “Vaccines made by white people are poisonous. If you thaw them and throw them away, you can’t breathe—the smell is awful. For diseases like measles, we use traditional methods; for other illnesses, some people go to the hospital.”
One mother belonging to this church reported being willing to vaccinate her children but feared retribution from her husband.
On the provider side, registered nurses (RNs) showed basic familiarity with the pentavalent vaccine, often referring to it by its local name, “DITECOQ.” While they had administered it repeatedly and understood it as a combination vaccine, most were unable to name its individual components or identify symptoms linked to its absence.
Notably, the RN at the VUVAMU Health Centre did not administer vaccines and had excluded them from their services.
Community Outreach Educators (COREs) participating in the study demonstrated greater familiarity with the DITECOQ vaccine and recognised its importance for child health. They stated: “DITECOQ protects against diphtheria, tetanus, whooping cough, and tuberculosis. However, we are focused more on campaign vaccines than routine ones, and we are not trained for routine vaccination.”
Mothers of vaccinated children confirmed that their children had been immunised and credited regular visits from RECOs (community health workers) for the uptake. Curiously, they reported having no knowledge of the pentavalent vaccine by name; they believed their children had received only BCG, DITECOQ doses 1, 2, and 3, OPV, and vitamin A.
Opportunity cost
From an economic perspective, many mothers of ZD children prioritised agricultural work over attending vaccination appointments. The majority reported financial hardship, stating that they were unable to afford even basic household necessities.
DISCUSSION
Summary of findings
This study aimed to identify the factors associated with zero-dose (ZD) children in the urban–rural health zone of Mont Ngafula 1, located within the Kinshasa city-province. A total of 406 children aged 12 to 23 months were included in the study.
The findings revealed several determinants associated with ZD children, notably:
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Age and religious affiliation of the mother or caregiver
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Main parental occupation
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Knowledge and awareness regarding vaccination
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Costs related to immunisation services and the perception of value for money
Socio-demographic characteristics
Among participants, boys comprised the majority (50.5%), with 52% having received at least one recommended vaccine. These figures align with previous studies by Asfaw, Ramakrishnan, Mathew, and Qadir,15–23 which similarly recorded a male majority.
Maternal age was found to be significantly associated with vaccination status; mothers aged 15 to 24 years were more likely to have ZD children.24,25
Religious affiliation also emerged as a contributing factor to non-vaccination. This finding is consistent with previous research.26,27 Ozigbuce and Olatosi B, for instance, found higher proportions of ZD children among Muslim families (25.2%) compared to Christian households (12.3%).28 A cross-sectional study using Demographic and Health Survey (DHS) data from Côte d’Ivoire, Ghana, Burkina Faso, Mali, Guinea, and Liberia also identified religion as a determinant of incomplete vaccination.29
However, literature reviews suggest that global religious doctrines do not explicitly oppose vaccination; resistance is often rooted in cultural and social norms.30,31 Notably, our study observed vaccine hesitancy among members of the VUVAMU Church and the Spirit Church FIKAMBI KAMBI, who demonstrated scepticism toward immunisation.
Contrary to national survey data from the DRC,7 which suggests increased vaccination coverage correlates with higher economic indices, our results showed that parents in paid employment were more likely to have ZD children. This may reflect time constraints associated with employment,32 or deeper gender-based inequalities within households.33–36
Knowledge of mothers and carers
Overall, 96% of respondents stated they had heard about vaccination an encouraging figure that serves as a protective factor. Yet, vaccine hesitancy and misinformation remain significant barriers.37–41
Although many mothers recognised the value of vaccination, interviews highlighted concerns about side effects, limited understanding, and intra-household disagreements. In some cases, mothers were informed but lacked support from male partners.33,42–47
Awareness of vaccine-preventable diseases (VPDs) varied. While 88.2% had heard of poliomyelitis, knowledge of other diseases covered by the pentavalent vaccine was lower: 47.8% for tetanus, 36.5% for whooping cough, 27.6% for diphtheria, 25.4% for hepatitis, and just 5.2% for Haemophilus influenzae type B.
The high awareness of polio may be attributed to recurrent vaccination campaigns and the MASHAKO initiative, which seeks to increase access to routine immunisation near family homes and improve vaccine availability.10
COREs (Community Outreach Educators) were more familiar with polio vaccination, often unaware of the broader scope of the pentavalent vaccine.
Our findings echo those of Drissa Skonate and Sory Ibrahima, who reported that maternal education plays a crucial role in vaccine literacy and uptake.11,48–52 Similarly, Nguefack Félicitée and Kobela Marie found that Bayam Sellam mothers remained vigilant with their children’s immunisation despite occupational demands.53,54
Interviews revealed continued uncertainty among parents about vaccine efficacy and the need for comprehensive post-vaccination care.
Opportunity cost and access to vaccination
Although immunisation services in the DRC are officially free, interviews suggest that perceived and indirect costs influence uptake. While the government provides vaccines to safeguard public health and promote productivity, many mothers prioritise economic activities such as farming over attending vaccination appointments.
Several mothers reported financial difficulties that affect their ability to pay for basic needs, suggesting that even minimal indirect costs can deter participation. household priorities and economic barriers.
The study found that 47% of mothers or carers of zero-dose (ZD) children and 36% of mothers or carers of vaccinated children prioritised household responsibilities over attending vaccination appointments. Many respondents reported that participating in vaccination sessions conflicted with essential domestic duties, prompting them to weigh perceived risks and benefits. These findings are consistent with previously published research.55,56
In terms of financial barriers, 45.3% of respondents stated that vaccinations required payment. Notably, mothers and carers who reported paying for vaccination services were significantly more likely to have ZD children, corroborating findings from earlier studies.57–59
Only 28.6% of mothers or carers expressed willingness to pay for vaccination services, a figure lower than that reported by Edmond Ndudi Ossai, who found rates of 54.5% in urban areas and 55.3% in rural regions.60
Respondents who supported the idea of the government proposing a fixed cost for vaccination sessions were significantly associated with higher vaccination rates highlighting this as a protective factor. This result mirrors findings by Ossai, who noted that willingness to pay was often influenced by dissatisfaction with service quality and the distance to health centres.60
While some mothers agreed to pay if the cost were officially set by the government, others resisted, arguing that immunisation should remain the responsibility of the state.
CONCLUSIONS
The study demonstrated that 72% of participating children had received the pentavalent vaccine. Analysis identified key factors associated with the remaining 28% of ZD children, including maternal age, religious affiliation, primary occupation, prior awareness of vaccination, knowledge of at least one vaccine-preventable disease (VPD), costs incurred for immunisation, and willingness to pay for services.
These findings underscore the need to enhance public awareness of VPDs and encourage uptake through mass media and community outreach effective channels for engaging a broad cross-section of the population.
Community Engagement and Perception of Vaccination, the government’s commitment to eliminating vaccine-preventable diseases is firmly rooted in its aim to improve population health outcomes. However, the study identified a misalignment between vaccinators and mothers or carers specifically regarding their knowledge and perception of vaccination.
Among mothers and carers in the health zone, 47.3% of respondents with ZD children and 36% with vaccinated children cited household responsibilities as a barrier to attending vaccination appointments. Additionally, 46% of ZD mothers/carers and 58% of those with vaccinated children reported prioritising other activities such as trading, tailoring, or agricultural work.
To reduce the prevalence of ZD children, engagement with religious leaders is essential. Their influence on community beliefs can play a crucial role in shaping attitudes towards vaccination. This calls for collaborative dialogue between government authorities, community leaders, and the wider population ensuring culturally sensitive interventions and sustainable solutions to improve child health and overall community well-being.
Funding
None.
Authorships
All authors contributed to the final draft and approved for submission.
Competing interests
The authors completed the ICMJE Disclosure of Interest Form (available upon request from the corresponding author) and disclose no relevant interests
Correspondence to:
Atila Mpula Nsongo
Lemba Kimbanguist Hospital Center, Kinshasa, Democratic Republic of Congo
atilansongo1@gmail.com