Factors associated with measles vaccination among children aged 12-59 months in Tambacounda commune, Senegal, in 2021

Tidiane Gadiaga^1,&, Mouhamadou Faly Ba², Mbouna Ndiaye³, Mamadou Sarifou Ba³, Siré Sagna⁴, Bayal Cissé⁴, Babacar Gueye¹, Ousseynou Badiane⁵, Elhadji Ba Konko Ciré⁶, Jean Louis Abdou Ndiaye⁶

 

¹Directorate of Planning, Research and Statistics, Ministry of Health and Social Action, Senegal, ²Institute of Health and Development, Cheikh Anta Diop University, Dakar, Senegal, ³Field Epidemiology Training Program, Senegal, ⁴Tambacounda Health District, Ministry of Health and Social Action, Senegal, ⁵Directorate of Prevention, Ministry of Health and Social Action, Senegal, ⁶Iba Der Thiam University of Thies, Thies, Senegal

 

 

^&Corresponding author
Tidiane Gadiaga, Directorate of Planning, Research and Statistics, Ministry of Health and Social Action, Senegal.

 

 

 

 

Although immunization is one of the most effective and cost-effective public health interventions to reduce mortality and morbidity, an estimated 1.4 million children die worldwide each year from vaccine-preventable diseases. [1]. Measles is one of the most contagious vaccine-preventable diseases [2]. Measles is a contagious febrile eruptive disease caused by a virus of the Paramyxoviridae family (Morbillivirus) and man is its only reservoir [3]. It is a disease with epidemic potential that poses a global public health problem. It affects more than 30 million children worldwide and remains the leading cause of death from vaccine-preventable diseases with nearly 875,000 deaths per year [4]. Measles vaccination has made a significant contribution to achieving the Millennium Development Goal of reducing under-5 mortality [5]. Despite the implementation of an expanded programme on immunization (EPI), parts of sub-Saharan Africa and even the world are suffering from large-scale epidemics, which prevent the eradication of measles [6]. These outbreaks have been attributed to insufficient vaccination rates in some settings [7] or to groups of unvaccinated people, who end up in countries with high vaccination rates [8]. In studies conducted in the African context, factors such as knowledge of planned doses of measles vaccine, birth order, long waiting times for immunization services, maternal education, postnatal counselling, and others were associated with the child's measles vaccination status [1]. Senegal, as part of its routine EPI, has adopted the World Health Organization (WHO) recommendations to immunize all children before their first birthday against the main vaccine-preventable diseases, including measles. The first dose of measles vaccine is recommended at nine (9) months of age and the second dose at 15 months up to 24 months of age. The country's goal was to vaccinate at least 90% of children under one year of age against measles. However, between 2019 and 2021, this target for MR1 vaccination coverage was not met in some districts of the country [9,10,11]. This was secondarily reflected in a measles outbreak in 16 of the country's 79 health districts in 2021. The health district of Tambacounda, which is located in the southeast of Senegal, has also experienced this measles epidemic with 16 cases in 2021 and an annual MR1 vaccination coverage of 82%. Low vaccination coverage was much more pronounced in the commune of Tambacounda (72%), which had also recorded 94% of the district's measles cases. In Senegal, studies have been conducted to estimate full immunization coverage and determine their associated factors [12,13,14]. However, to our knowledge, no studies have been conducted in this context and in this direction with a specific focus on measles vaccines. Therefore, we set out to determine the MR1 vaccination coverage of children aged 12 to 59 months in the commune of Tambacounda and to identify the determinants related to this vaccination coverage.

 

 

Study Setting

 

The commune of Tambacounda is located in the Tambacounda health district and the eponymous Tambacounda region. Tambacounda region is located in the south-east of the country, and is the largest region but hosts only 5.5% of the population, making it the region with the lowest land use. The health district of Tambacounda has an area of 11,416 km² with an estimated population in 2021 of 305,801 inhabitants, and a natural increase rate of 2.7%. The district has six communes, including Tambacounda, which has 46% of the population with 142,307 inhabitants for an area of 7,755 km², i.e. a density of 19 inhabitants/km². In terms of health, the municipality of Tambacounda has the highest number of the health facilities in the district with 1 reference health center and 7 health posts. All these health facilities offer routine immunization services. Each of them has a vaccination unit headed by a state nurse. The head nurse and team conduct both fixed and outreach vaccination strategies to neighbourhoods to make it easy for the entire population to access vaccination in the interests of equity. During these different strategies, all the antigens of Senegal's Routine Expanded Immunization Program are delivered, namely BCG, OPV, Pentavalent, VAT, MR1, AAV and MR2 in accordance with the six-contact vaccination schedule. However, the measles vaccine series is given in children less than 2 years of age in 2 contacts, at 9 months of age or older and at 15 months of age or older. Over the past three years, annual MR1 vaccination coverage reported by the various vaccination units in the municipality of Tambacounda varied between 69% in 2019, 73% in 2020 and 72% in 2021.

 

Study design and period of study

 

This was an analytic cross-sectional study in the commune of Tambacounda, conducted from 1 to 6 August 2022.

 

Study population

 

These were children between the ages of 12 and 59 months living in the municipality of Tambacounda. The survey population consisted of mothers and or caregivers of these children who resided in the commune of Tambacounda.

 

Survey Units: They were mothers and or caregivers of children aged 12 to 59 months from the 40 neighbourhoods of the commune of Tambacounda.

 

Statistical Units: These included children aged 12 to 59 months and mothers and caregivers of children aged 12 to 59 months in the sample.

 

Eligibility criteria

 

Inclusion Criteria: We included in the study any child that was born between July 31, 2017, and July 31, 2021, residing in the commune of Tambacounda for more than one year.

 

Exclusion criteria: We excluded children whose mothers and/or caregivers did not wish to participate in the study; those whose mothers or caregivers were not available.

 

Sample size calculation

 

For the household survey, the sample size was calculated using Schwartz's formula [15]:

 

 

The parameters in play are defined as follows: -

 

- n: Sample size; -

 

- t: Margin coefficient deduced from the confidence level (95% in our case, t=1.96) -

 

- e: Margin of error that we give ourselves for the quantity we want to estimate (5% in our case); -

 

- p: MR1 coverage equal to 72% [11]; -

 

- A: Non-response rate (10%).

 

Applying these different parameters and considering the cluster effect of 2, the minimum sample size was 682 mothers or caregivers to be surveyed.

 

Sampling

 

The method used was based on a three-stage stratified sampling approach.

 

The first stage was made up of the health posts of the health centre of the commune of Tambacounda, with exhaustive recruitment. The municipality of Tambacounda has seven (07) health posts and a health center with areas of responsibility.

 

The second level was made up of the different districts of the commune of Tambacounda. We have listed all the health facilities and noted their respective populations as well as the cumulative population of the commune of Tambacounda. The target population (children aged 12 to 59 months) was estimated at 15.15% of the total population. For each health facility, we determined its target population of 12 to 59 months and its demographic weight according to the total target of the municipality of Tambacounda. We listed all the forty (40) neighbourhoods of the commune. An exhaustive recruitment of the 40 neighbourhoods is done for the survey. The number of mothers or babysitters to be surveyed per neighbourhood is determined according to the demographic weight of the neighbourhood in the municipality of Tambacounda.

 

The third stage consisted of households to be visited. To determine the first child to be surveyed, we proceeded as follows: for each structure, we listed all the neighborhoods in the area of responsibility. All the neighborhoods are to be surveyed and once in the neighborhood, the drawing of homes and children was done on the ground and always at random. The investigator would stand in the center of the neighborhood and throw a pen or pencil in the air. The tip of the pen indicated the direction to follow. He counted the number of gates or concessions and always visited the second concession on the right from his position. In the first house chosen, the investigator was looking for a child who met the criteria. The questionnaire was then administered to the mother or guardian who had been in charge of the child since 6 weeks of age. The investigator adopted the same strategy for all children in that concession who met the predefined criteria before moving on to another concession. From this first concession, the investigator will progress step by step on the same row, taking care to mark with chalk the sign of the cross "X" on the gate or wall of the house under investigation until he finds the number of children required for each neighborhood. If the investigator completes all of the neighborhood's concessions and the required number of children is not reached, he or she will supplement with the neighboring neighborhood following the same predefined approach. Faced with this situation, the investigator will have to verify that another investigator has not visited this additional concession (Figure 1).

 

Data collection

 

Collection tool and data sources: Data were collected using a questionnaire consisting of five parts: (i) identification of the health facility, the interviewer, the village or neighbourhood; (ii) socio-demographic characteristics of mothers or caregivers, (iii) information about the child such as age, sex, vaccination status; (iv) mother's or babysitter's knowledge of immunization; and (v) their attitudes and practices towards vaccination.

 

Method of collection

 

Forty (40) interviewers, who had at least a secondary middle education and spoke the local language, were selected and trained in one day on the administration of the questionnaire. The questionnaire was tested on the same day in a peri-urban area in a district of the neighbouring municipality. A debriefing was organized in the afternoon with the investigators and members of the core team to share the difficulties and take corrective measures.

 

Subsequently, the collection was carried out using an interview administered questionnaire among mothers and/or caregivers of children aged 12 to 59 months and the was used to collect data on child´s vaccination status.

 

Data on the child's vaccination status was collected from the immunization record/vaccination card (if available) or from the immunization history reported by the mother or babysitter. The dependent variable was vaccination with the first dose of measles and rubella vaccine (MR1) given between 9 and 23 months of age. The independent variables collected in the quantitative survey were conceptualized according to the model of Andersen and Newman [16]. They included:

 

- Predisposing factors: age of the mother and/or caregiver, marital status, level of education, main activity, knowledge of the target disease, knowledge of the age of initiation of MR vaccination and number of contacts with the MR vaccine, sex of the child, sibling status.

 

- Facilitating factors: place of residence of the mother and/or caregiver, respondent, place of vaccination, distance between home and vaccination site, use of means of transport for vaccination, profile of the vaccinator, quality of the information provided by the vaccinator.

 

- Need factors: Booklet availability, visibility of BCG scar in children, suitability of vaccination day, mother/caregiver´s satisfaction with immunization services, COVID-19 safety. -

 

Statistical Analysis

 

The data collected was entered into the Epi Info software version 7.2 and exported to R software version 4.2.1 for data analysis. A descriptive study with univariate analysis was used to describe the parameters of quantitative (mean, standard deviation, median, extent, extremes) and qualitative (absolute and relative frequencies) variables. Then, we carried out an analytical study with bivariate analyses. To study or assess the relationships between the different variables, we tested Chi2 with a cut-off p of 0.05. A multivariate logistic regression analysis was performed using a backward stepwise procedure. Variables showing significant association (p<0.05) in bivariate analysis were included in the initial model. The final model retained variables with a significance threshold of p<0.05. Association strengths were measured by adjusted odds ratios (aOR) with their 95% confidence intervals.

 

Ethical considerations

 

We received the approval of the Tambacounda district chief medical officer for the survey. This investigation was carried out in strict compliance with the rules of medical conduct and ethics. It was also done anonymously. No information was collected without the free and informed consent of the mothers or caregivers. Catch-up vaccination was proposed, if always possible in case of incomplete vaccination status. The results of the survey were used to develop a problem-solving plan.

 

 

The study was carried out in the commune of Tambacounda, in the district of the same name, on a sample of 714 children aged 12 to 59 months. A total of 714 women were surveyed having been in contact with immunization services at least once in the past. The mean age of the women surveyed was 28.9 years with a standard deviation of 6.5 years. The youngest age for these women was 18 years and the maximum age was 51 years. Women within the 25 - 35 years age were the majority (52.0%) and 672 (94.1%) were biological mothers of the children. 48.3% of the women surveyed were uneducated and only 25.5% of them had an income-generating activity. Only 43.1% of respondents knew the age of administration of the first MR vaccine and 42.1% knew the number of contacts with the MR vaccine (total number of doses of vaccine recommended in the vaccination schedule) (Table 1).

 

348 women (48.7%) received information about vaccination from health workers. Radio and television sources of information returned in 149 (20.9%) and 81 (11.3%) responses from the women surveyed, respectively. Of the women surveyed, 312 (43.7%) reported Adverse event post-immunization (AEPI), and 87.2% (324/372) of them resorted to self-medication following the appearance of an AEPI in the child. Only 12.2% (45/372) of them brought the child back to health facilities following an AEPI. The mean age of the child was 33.7 (SD 14.1) months, The minimum age was 12 months and the maximum age was 59 months. The were more male children at 52.0%. BCG scar was present in 84.9% of the children.

 

Of the women surveyed, 8.0% felt that their child had developed a confirmed measles episode or had shown suspicious signs of measles (Table 2).

 

Of all children , 80.0% (571) received the first MR1 dose. Of the targeted children aged 15 months and older (712), only 58.6% are fully vaccinated against measles (had received both recommended doses of measles vaccine (MR1 and MR2)).

 

Of the women surveyed, 50.4% of them travelled at least 200 m to get to a vaccination unit. A majority (44.3%) used transportation vehicles (cars, motorcycles, or bicycles) to get facilities. Only 3.5% of women had their children vaccinated during fixed strategies that moved to the neighborhood (mobile outreach) while 68.5% were vaccinated by Community Health workers (CHWs, matrons). However, the vaccinators provided limited vaccination systematic information to the children´s mothers/caregivers. Only 56.2% of women were informed about the date of the next appointment by the vaccinator. Among mothers and/or caregivers, 88.8% felt that the day of vaccination was convenient for them and 94.1% responded that the vaccination was free of charge at the vaccination units level. 71.3% of women knew the age of first MR vaccination.

 

In relation to immunization services, 82.6 per cent of women were satisfied with the reception, 79.5 per cent with the waiting time and 78.4 per cent with the advice on the child's vaccination. Despite the COVID-19 context in 2021, only 7.1% of women surveyed had missed their appointment due to COVID-19 (Table 3). Fear of COVID and rumours about the disease were the majority causes with 36.6% and 22.5% respectively of the 51 caregivers.

 

In the bivariate analysis, several factors were significantly associated with MR1 vaccination uptake. Knowledge of vaccination importance (OR=3.67, 95% CI: 2.33-5.76), knowledge of MR contacts (OR=2.35, 95% CI: 1.58-3.57), mother's education (OR=1.69, 95% CI: 1.17-2.46), and satisfaction with reception (OR=1.76; 95% CI: 1.12-2.72) were positively associated with MR1 vaccination. However, distance to vaccination site (OR=0.71; 95% CI: 0.49-1.02) and history of measles (OR=0.47; 95% CI: 0.26-0.87) were negatively associated with vaccination (Table 4).

 

At multivariate analysis only two factors remained significantly associated with MR1 vaccination after adjustment: knowledge of the importance of measles vaccination and knowledge of the number of MR contacts. Mothers who knew the importance of vaccination were three times more likely to have their child vaccinated against measles (aOR = 3.00; 95% CI: 1.88 - 4.79). Similarly, mothers who knew the number of MR recommeded doses were nearly twice as likely to have their child vaccinated (aOR = 1.91; 95% CI: 1.25 - 2.91). Women's satisfaction with reception was no longer significantly associated with vaccination after adjustment (aOR=1.05, 95%CI: 0.72-1.55) (Table 5).

 

 

This study conducted in the commune of Tambacounda revealed an MR1 vaccination coverage of 80.0% among children aged 12-59 months. The main factors associated with better vaccination coverage were knowledge of vaccination importance and knowledge of the number of MR contacts/doses. These results highlight the importance of strengthening mothers' health education, particularly regarding specific aspects of measles vaccination.

 

The women surveyed were mainly the biological mothers of the children (94.1%). Niang [12] and Tine [17] in their studies in Senegal found similar proportions with 96.9% and 93.1% respectively. Of the women in this series, 51.7% were in school compared to 37.3% in Niang's work. However, our study found a statistically significant association between MR1 vaccination and maternal and/or caregiver schooling. Children of educated mothers were almost twice as likely to be vaccinated against measles compared to children of uneducated mothers. With schooling, women's knowledge of the MR vaccine and its benefits increases; For example, educated women are much more likely to bring their children for measles vaccination. This thesis is further supported by our work because children whose mothers had knowledge of the importance of vaccination were almost 4 times more likely to be vaccinated against measles than those who did not. Also, in our study, children whose mothers knew the number of contacts of the MR antigen were almost 3 times more likely to be vaccinated against measles than other children. The same was true for the knowledge of the age of first MR contact. The implementation of important immunization communication activities in the district's annual work plan could explain these results. In our series, the proportion of mothers and caregivers without income-generating activities was 74.5%. Tine [17] and Seck [18] in their studies in Senegal had found approximately the same results on similar populations with 79% and 89.4% respectively. Children of mothers with income-generating activity were almost twice as likely to be vaccinated against measles. Seck [18] and Niang [12] found the same associations with full vaccination with all antigens. This association in these different studies could be linked to the availability of financial resources among women to bring their children to the level of vaccination units.

 

In this study, 8.0% of children had confirmed measles or suspicious signs of measles. This was in line with the epidemiological situation in the district, which was in a measles epidemic at the time of the survey [19]. Indeed, in developing countries such as Senegal, measles primarily affects children under 5 years of age [20] who were our target in this survey. There was also an association between the presence of confirmed measles or suspicious signs of measles and MR1 vaccination. Children with confirmed measles or suspicious signs were nearly 2 times more likely not to be vaccinated against measles. This partly enhances the protective effect of the MR vaccine against measles. Since the 1990s, there has been evidence in several countries that measles transmission has been stopped through the implementation of routine and supplemental immunization programs with MR vaccine at coverages greater than 95% [21].

 

the study showed more than half of the women surveyed travelled more than 200 m to get their child vaccinated against measles. There was also a statistically significant association between distance travelled and measles vaccination. The children of women who walked less than 200m were more likely to be vaccinated against measles. This shows the importance of the accessibility of vaccination units to ensure that children benefit from the act of vaccination against measles. Mezoe [22] in his work in Cameroon had also demonstrated that geographical accessibility was a factor favouring vaccination. It had proven that the greater the distance between the child's home and the post, the less likely the child was to be fully vaccinated. Mothers and babysitters in this series walked to vaccination units in 55.7% of cases. Because of the proximity to the immunization service, children whose mothers walked to health facilities were more likely to be vaccinated against measles. Bassoum [23] in his study on vaccination against Hepatitis B at birth, Poliomyelitis and tuberculosis in Podor, in northern Senegal, found that 61.9% of women walked to vaccination services.

 

In Senegal, vaccination is free, but there are still some mothers and babysitters who cover some of the costs related to vaccination. This is the case of our study where 5.9% of women felt that the vaccination service was paid. However, these expenses are most often related to the transportation or purchase of medications, and not to the act of vaccination. Tine [17] in his work in Popenguine, Thiès found the same results with 1.2% of women who said they had spent money on vaccinating their children. According to Senegal's national guidelines, vaccination is an act devolved to qualified technical personnel. However, the results showed that 68.5% of the women surveyed felt that their children were vaccinated by community health workers. This was not the case in Tine's work in Popenguine where 71.2% of women felt that their children were vaccinated by qualified personnel [17]. The lack of qualified human resources in areas far from the Senegalese capital is one of the factors explaining this contrast between the two districts.

 

The satisfaction of the mother and/or caregiver with the provision of immunization services is an important factor in encouraging the latter's attendance at immunization units. Our work showed that women's satisfaction with admission to immunization services improved vaccination coverage at MR1. Tine [17] in his study, found the same association between satisfaction with reception and complete vaccination coverage. Satisfaction with wait time also led to good MR1 vaccination coverage. Other studies such as those by Niang and Tine also found the same association.

 

The last two years have been marked by the COVID-19 pandemic, which has led to low attendance at health facilities by women in Senegal. However, the proportion of women who missed their appointments due to COVID was low.

 

 

This study, which aimed to identify the factors associated with measles vaccination among children aged 12 to 59 months in the commune of Tambacounda, highlighted key points on which action will be needed to strengthen measles vaccination. Thus, to increase MR1 vaccination coverage among children, interventions should focus on strengthening mothers' knowledge about vaccination, particularly regarding two key aspects: the importance of measles vaccination and the recommended number of vaccine doses. This emphasizes the need for targeted health education and communication strategies through community health actors and vaccinators to enhance mothers' understanding of these critical aspects of the measles vaccination program. However, with the measles epidemic context in the district, a study on the quality of the MR vaccination service offer at the VU level must be carried out to better understand all the determinants related to measles vaccination in Tambacounda.

 

 

The authors declare no competing interests.

 

This research was funded by the Ministry of Health and Social Action of Senegal through the Tambacounda health district.

 

 

Funding acquisition: Tidiane Gadiaga, Siré Sagna. Methodology: Tidiane Gadiaga, Mamadou Sarifou Ba, Mbouna Ndiaye, Mouhamadaou Faly Ba Elhadji Ba Konko Ciré, Jean Louis Abdou Ndiaye. Project administration: Tidiane Gadiaga, Siré Sagna, Bayal Cissé, Elhadji Ba Konko Ciré, Jean Louis Abdou Ndiaye. Software: Tidiane Gadiaga, Mbouna Ndiaye, Mamadou Sarifou Ba, Mouhamadou Faly Ba. Supervision: Tidiane Gadiaga, Samba Cor Sarr, Bayal Cissé, Elhadji Ba Konko Ciré, Jean Louis Abdou Ndiaye. Validation: Tidiane Gadiaga, Elhadji Ba Konko Ciré, Samba Cor Sarr, Babacar Gueye, Jean Louis Abdou Ndiaye Writing – original draft: Tidiane Gadiaga, Mouhamadaou Faly Ba Elhadji Ba Konko Ciré, Jean Louis Abdou Ndiaye. Writing – review & editing: Tidiane Gadiaga, Siré Sagna, Ousseynou Badiane, Samba Cor Sarr, Babacar Gueye, Elhadji Ba Konko Ciré, Jean Louis Abdou Ndiaye

 

 

Thanks go to the women of the commune of Tambacounda, the head nurses, the major of the Tambacounda referral health center, the investigators and members of the district management teams of Tambacounda without forgetting the members of the district health development committee who financed the survey.

 

 

Table 1: Characteristics of Mothers/Caregivers (n=714)

Table 2: Characteristics of the Target Child (n=714)

Table 3: Childhood Immunization Characteristics (n=714)

Table 4: Factors Associated with Measles Vaccination at bivariate analysis (N=714)

Table 5: Multivariate analysis

Figure 1: Flowchart sampling

 

 

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