Zero-dose children who never receive a single vaccine are also more likely to miss out on crucial primary health care services.
Gavi Alliance
by Priya Joi
10 November 2021
What is the research about?
The number of children in low and lower middle income (LMIC) countries who are given routine immunisation has risen significantly in the past two decades,
but there are still a large number of children — 17 million in 2020 — who never receive a single vaccine.
17 million of Children (2020) never receive a single vaccine.
These are zero-dose children, and they are likely to also be unable to access primary health care services, although there have been no studies with data from multiple countries analysing this linkage.
They found that unvaccinated children and their mothers were systematically less likely to receive other primary health care interventions, particularly for antenatal visits and access to institutional delivery.
What did the researchers do?
Researchers from Gavi and the Federal University of Pelotas, Brazil, investigated the overlap between not being vaccinated with routine immunisations and failing to receive other primary health care services.
They analysed data from more than
- 200,000 infants aged 12 to 23 months
- between 2010 and 2019
- from 92 LMICs.
They looked at six vaccination indicators based on the bacille Calmette-Guérin (BCG), polio, diphtheria-tetanus-pertussis (DTP) and measles vaccines and their overlap with primary health care indicators, including at least four antenatal care visits, institutional delivery, careseeking for common childhood illnesses or symptoms and place for handwashing in the home.
The researchers used lack of DTP vaccines as a proxy for zero-dose children, as DTP is offered almost exclusively through routine immunisation touchpoints and is the operational indicator for zero-dose children in the Immunisation Agenda 2030.
What did they find?
They found that unvaccinated children and their mothers were systematically less likely to receive other primary health care interventions, particularly for antenatal visits and access institutional delivery.
Mothers of zero-dose children are 46% less likely to have four or more antenatal visits compared to mothers of vaccinated children. Lack of DTP vaccination was also associated with lower coverage of institutional delivery (43% less likely), careseeking behaviour (18%) and handwashing facilities (36%). These associations were more pronounced for the poorest households.
The researchers also found that using access to DTP-containing vaccines as an indicator is helpful as it “helps to identify children with limited access to health services since it is offered almost exclusively through routine immunisation touchpoints required for ensuring full immunisation”.
What does this mean?
Families whose children have no access to vaccination are missing out on crucial primary health care services that affect both mothers and children, and offers an opportunity for integrated service delivery to reduce inequity.
Generally, these families are also worse off financially than families who do have access to vaccines, which indicates that specific efforts need to be made to reach them as they are less likely to have the capacity to reach out for healthcare.
Identifying and reaching zero-dose children is likely to be critical to tapping into families who are missing out on important primary health care interventions.
Identifying and reaching zero-dose children is likely to be critical to tapping into families who are missing out on important primary health care interventions.
Originally published at https://www.gavi.org.
ORIGINAL PUBLICATION
Finding Children with High Risk of Non-Vaccination in 92 Low- and Middle-Income Countries: A Decision Tree Approach.
MDPI Vaccines
Vaccines, 13 Jun 2021
Thiago M. Santos * , Bianca O. Cata-Preta , Cesar G. Victora and Aluisio J. D. Barros
International Center for Equity in Health, Federal University of Pelotas
Abstract
Reducing vaccination inequalities is a key goal of the Immunization Agenda 2030.
Our main objective was to identify high-risk groups of children who received no vaccines (zero-dose children).
A decision tree approach was used for 92 low- and middle-income countries using data from Demographic and Health Surveys and Multiple Indicator Cluster Surveys, allowing the identification of groups of children aged 12-23 months at high risk of being zero dose (no doses of the four basic vaccines-BCG, polio, DPT and measles).
Three high-risk groups were identified in the analysis combining all countries. The group with the highest zero-dose prevalence (42%) included 4% of all children, but almost one in every four zero-dose children in the sample.
It included children whose mothers did not receive the tetanus vaccine during and before the pregnancy, who had no antenatal care visits and who did not deliver in a health facility.
Separate analyses by country presented similar results.
Children who have been missed by vaccination services were also left out by other primary health care interventions, especially those related to antenatal and delivery care.
There is an opportunity for better integration among services in order to achieve high and equitable immunization coverage.
There is an opportunity for better integration among services in order to achieve high and equitable immunization coverage.
4. Discussion (excerpted from the full version of the paper)
The pooled decision tree indicates a clear message: the children at a higher risk of being zero dose are the ones who themselves and whose mothers have been left out by other health services and interventions, in particular antenatal care.
The fewer health services and interventions the child/mother pair received, the higher the risk that the child has not been vaccinated. The triple exposed children (those whose mother did not receive any doses of the tetanus vaccine, who did not have any antenatal care visits and whose delivery was not in a health facility) had an alarming zero-dose prevalence of 42%. But it is important to stress: no causal relationship is established by the decision tree. The analysis only indicates that both phenomena have happened in the same household.
The fact that the triple exposed children were only a small percentage of the sample (4%), but they accounted for one in every four zero-dose children indicates:
(1) the opportunity they represent for targeted interventions and
(2) how challenging it is to reach them, as they and their mothers have already been left out by vaccination, antenatal care, and delivery services. This result corroborates the current recommendation by the IA2030 to “Encourage greater collaboration and integration within and beyond the health sector,” reinforcing the importance of integration between primary health care services in order to increase efficiency and reach those who are being left out by multiple basic interventions [3].
It is no surprise that the first indicator selected by the tree was the mother not having received any doses of the tetanus vaccine, which could evidence similar challenges in effectively vaccinating mother and child, involving vaccine supply, logistics, application, monitoring, and long-term predictable funding [18].
Both vaccination and antenatal care services failed to reach and vaccinate these mothers during and before the index pregnancy, which contributes to the burden of maternal and neonatal tetanus [19].
Furthermore, one in every four children of these mothers was also zero dose, therefore failing to achieve both short and long-term protection against tetanus for the child.
The lack of any antenatal care visits can also function as an indicator of families that are harder to reach by health services, but it can also have an impact on the future vaccination of the child.
Mothers with more antenatal care visits have more opportunities to receive positive messages by healthcare providers regarding the advantages of vaccinating their soon-to-be-born child, increasing awareness of the benefits and safety of vaccines and sharing information such as the appropriate place and time for vaccination [20].
The child not being delivered in a health facility can have a more direct link with the zero-dose status.
The WHO recommends that in countries with high burden of tuberculosis a single dose of the BCG vaccine should be given at birth to all healthy neonates [21] and 152 LMICs have a policy of universal neonatal vaccination at birth or at the first week of life [22]. This is in accordance with our results: among children whose mothers have not been vaccinated against tetanus and who have had zero antenatal care visits, those who were born in a health facility had a zero-dose prevalence of 23% while those who were not had almost double the prevalence (42%).
Our equity analyses showed that the groups of children at higher risk of being zero dose were significant and incrementally poorer, more rural and with less educated mothers.
This is in line with the literature, as children in those conditions are less likely to be vaccinated [5] and their mothers are also less likely to receive qualified antenatal care [23]. This result further indicates the level of vulnerability of the children in the higher risk groups, as their socioeconomic condition has also been associated with lower medical-treatment-seeking behavior [24], worse nutritional status [25], and higher mortality among unvaccinated children [26].
In 2002, the WHO and the UNICEF launched the “Reach Every District” (RED) strategy, an initiative that promotes the prioritization of districts with poor access and utilization of vaccination services [27], with reports of increased vaccination coverage [28] and detection of vulnerable populations [29,30] after the adoption of the RED strategy.
A proposed improvement to the RED strategy is the “reach every community” approach, with a focus on facility-level planning, monitoring of community access and utilization of vaccination services, local communication strategies and health networks that should allow for the tailoring of vaccination delivery systems according to the specific necessities of vulnerable communities [29].
Those strategies are an opportunity to promote other maternal, newborn, and child health (MNCH) services, since community involvement can help to identify newborn and pregnant women that could be targets for those services [31]. An example is the inclusion of a wider MNCH, environmental health, and water and sanitation package by planners involved in the application of the RED strategy in the Byanzurkh District in Mongolia, since they determined that both vaccination and MNCH services shared similar barriers in the district (distance, level of education, and poverty) [30].
The strengths of this paper include: the multi-country approach, with the inclusion of 92 nationally representative surveys and the resulting large sample size; the choice of zero dose as the studied vaccination outcome, therefore focusing on the most vulnerable children; the national profiles created, with the prevalence of key indicators and national decision trees; and the novel use of decision trees. They are a versatile tool that can be used for identifying risk groups of other outcomes in the context of global and public health. The CART implementation, in particular, can thrive in the large sample sizes that are quite common in the field. Furthermore, it allowed for the inclusion of 17 indicators of vulnerability without previous specification of cut-off points and interactions, dealing with the complex intersections between them.
Unfortunately, we were able to identify risk groups for only 25 out of the 92 countries studied.
The tree’s inability to identify risk groups is most likely due to three factors (individually or in combination): the indicators selected for the analyses failing to discriminate zero-dose children from the remaining children in the sample, low sample size, and low zero-dose prevalence. The last two factors impact the algorithm’s ability to create groups that are large enough and with enough zero-dose children to be maintained during tree creation, especially with our imposed limitation of at least 50 children in each group. This is supported by the fact that countries where risk groups were identified had a median zero-dose prevalence more than six times higher and a median sample size more than 60% higher than the countries with no risk groups identified. Furthermore, countries with really low zero-dose prevalence may not have well-defined risk groups from a population perspective and the remaining children might only be reached by population level interventions. Nevertheless, for the 25 countries where risk groups were identified, the result was similar to the pooled tree analysis: antenatal care visits, delivery in a health facility, and tetanus vaccination were the most common indicators selected by the trees; the last one together with the wealth indicator.
There are several limitations to these analyses.
First, since children with missing information in a vaccine are considered as non-vaccinated, the zero-dose prevalence might be overestimated. As a sensitivity analysis, we calculated the pooled zero-dose prevalence removing all zero-dose children with missing information for any vaccine, resulting in a prevalence of 7.4% (7.1–7.6%). Among the top five countries, South Sudan and Congo DR had 21% and 18% of all zero doses from children with missing information in at least one vaccine. Although this is far from ideal, it follows the current recommendation by the WHO on how to treat missing information for vaccination records [9] and is a more conservative approach, considering the risks of non-vaccination.
Second, although we were successful in identifying zero-dose risk groups in the pooled analysis, 67% of all zero-dose children in the sample were classified as part of the lowest risk group. This may be due to indicators of vulnerability not included in the analysis or due to the fact that some children do not belong to a specific and well-defined risk group. Further investigation is necessary — possibly using other indicators — as well as a general strengthening of health services, combined with population interventions, in order to ensure that those children are not missed.
Third, the highest zero-dose prevalence found in a risk group from the pooled tree was 42%. One could argue that this is a low prevalence for a more traditional application of a classification algorithm, especially if used as a prediction tool. Considering that our main goal was to identify the risk groups, not to create predictions, and since zero-dose prevalence tends to be really low in most countries, we believe that 42% represent a significantly high prevalence from a public health perspective.
Fourth, the choice of using a double misclassification cost was arbitrary and the final tree is dependent on that choice. As a sensitivity analysis, we tested other adjustment weights (1, 3, 4, and 5). For 1, no risk groups were identified. For 3 to 5, a very similar tree was created, but the last split (if the child was born in a health facility) was not present. Therefore, the final message remains valid, but with the caveat that the last split should be interpreted with caution.
5. Conclusions (excerpted from the full version of the paper)
“Leave no one behind” is an opportunity to reach not only those who have been left out by vaccination, but also by other primary healthcare services.
The children at higher risk of being zero dose are also the ones whose mothers were left out by antenatal care, delivery, and vaccination services.
Those children are also poorer, more rural, and their mothers less educated.
The children at higher risk of being zero dose are also the ones whose mothers were left out by antenatal care, delivery, and vaccination services.
Those children are also poorer, more rural, and their mothers less educated.
Further integration of primary health care services and targeted interventions toward the most vulnerable communities are necessary in order to achieve the Sustainable Development Goals and the Immunization Agenda 2030.
Further integration of primary health care services and targeted interventions toward the most vulnerable communities are necessary …
Originally published at https://europepmc.org
Originally published at https://europepmc.org
