Introduction
Since January 2020, the COVID-19 pandemic has been responsible for more than 6 million deaths worldwide, forcing many countries to take unprecedented measures to reduce its burden [
1]. Efforts to reduce transmission have had indirect consequences on health systems, including disruption of supply chains, reduced mobility and access to services, closure of health facilities, and fear of visiting health facilities, all of which have likely worsened endemic disparities in access to healthcare services [
2]. In many countries, logistical barriers and measures to reduce the risk of COVID-19 transmission have adversely affected door-to-door campaigns, and community-based programmatic efforts have been similarly disrupted [
3,
4].
On March 26, 2020, the World Health Organization (WHO) called for a temporary suspension of mass vaccination campaigns, except for routine immunization programs in areas where risk of COVID-19 transmission was very low or negligible [
5]. Since infant and child vaccinations are amongst the most successful public health interventions in low- and middle-income countries (LMICs) in terms of number of deaths averted per year [
6], limiting these efforts raises serious public health concerns. Several countries have been faced with the public health dilemma of interrupting community-based immunization campaigns to control the transmission of COVID-19, increasing the risk of an epidemic rebound of childhood diseases normally kept under control by vaccinations. A similar situation was observed during previous disruptions of vaccination campaigns; notably, infant immunization coverage decreased during the Ebola outbreak in West Africa, which may have contributed to the increased incidence of measles in the region in the following years [
7‐
10].
Following predictions that such an interruption in routine vaccination efforts would likely put ~ 80 million children at risk of vaccine-preventable diseases (such as poliomyelitis, measles, and diphtheria) and could result in a 45% increase in child mortality, the WHO and other organizations rapidly recommended to resume vaccination campaigns [
11‐
13]. Despite this, the disruption caused by the pandemic has been associated with an estimated decline in global immunization coverage from 86% to 2019 to 81% in 2021, the lowest since 2009 [
3,
14,
15]. Analyses of data from routine health information systems in several African, Asian, and South American countries have confirmed reductions in the number of children vaccinated at health facilities immediately after the onset of the pandemic [
16‐
21].
These predictions and assessments from routine health information systems are likely biased for a number of reasons; for example, due to health personnel shortages and increased workload during the pandemic, data entry and transmission may have been reduced or interrupted. In addition, routine health information systems provide little information confirming whether infant immunization is actually administered, since vaccination data received during door-to-door visits of households are not always entered into health information systems. Further complicating matters, most studies have investigated only the short-term repercussions of the pandemic, focusing on the critical situation in 2020. For many LMICs, empirical, population-based evidence on vaccination coverage since the COVID-19 pandemic remains scarce.
Our study was designed to investigate changes in vaccination coverage in infants in rural Burkina Faso during the COVID-19 pandemic. While there have been reports of partial and transient disruptions of immunization services in the country [
22], there is no empirical evidence on whether the pandemic has affected infant immunization coverage. Using panel data collected just before (2019–2020) and during (2021) the pandemic, this study’s primarily aim is to investigate the repercussions of the COVID-19 pandemic on infant vaccination coverage in Burkina Faso. The secondary objective is to examine long-term trends in vaccination coverage between 2010 and 2021, with the working hypothesis that the pandemic would decrease the coverage of age-appropriate complete vaccination and reverse the upward trends observed since 2010 [
23]. This study is the first to offer an integrated perspective on the history of vaccination coverage and assess the lasting effects of COVID-19 on age-appropriate vaccination in infants in rural Burkina Faso.
Discussion
This study aimed to investigate the effects of the COVID-19 pandemic on age-appropriate full vaccination coverage amongst infants under 14 months of age in rural Burkina Faso, using repeated surveys in a panel of households. Our results showed that on average, coverage increased from 50% before the pandemic to 65% during the pandemic (odds ratio = 1.8, 95% confidence interval [1.14–2.85]). Compared to prior research [
29], our study provides a more nuanced and in-depth understanding of the impact of the pandemic on vaccination coverage in rural Burkina Faso. By considering the effects at the district level and including a mixed effects model, our study provides a more comprehensive picture of the effects of the pandemic on vaccination coverage and highlights the importance of considering local context and variation when evaluating public health interventions.
The observed increase in vaccination coverage contrasts with our initial working hypothesis and with previous studies [
16‐
21] that showed a decline in routine immunization rates during the COVID-19 pandemic. Notably, a systematic review of 26 studies conducted in 2022 found that all but five showed significant reductions in immunization coverage during the pandemic [
31]. Using a design similar to the one used here, a recent study in Peru found an 8% decrease in the immunization rate amongst infants aged 12–23 months between 2019 and 2021 [
32]. Several dynamics likely combined to trigger this phenomenon, including supply difficulties, interruptions in vaccination campaigns, and reduced access to healthcare. In some settings, the COVID-19 pandemic was positively associated with infant vaccination rates: One study found a 35% increase in child vaccination rates in Kenya during the pandemic [
33]. Although the reasons are not fully understood, some argue that pandemics can have a positive influence on vaccination coverage due to heightened public awareness and more frequent contact with healthcare services [
33,
34]. In Burkina Faso, after the suspension of all door-to-door immunization campaigns on March 27, 2020, a small outbreak of circulating vaccine-derived poliovirus led the authorities to rapidly resume public awareness and mass immunization campaigns in July 2020 [
35]. The determination of health authorities to maintain and even strengthen vaccination activities and awareness despite the pandemic may have contributed to an increase of immunization rates. In the present study, the majority of respondents reported feeling little to no threat of contracting COVID-19 through a vaccination program, which may have helped mitigate some negative impacts of the pandemic.
Our study revealed substantial variability in the effects of the pandemic across districts. While some districts experienced a significant increase in vaccination coverage, others observed no change or even a decrease. Our results showed a growing range of predicted probabilities over the period, and the pandemic arguably increased the non-stationarity of the observed trends. Al-kassam-Cordova et al. (2023) reported regional disparities in full-vaccination coverage amongst 12–23-month-old infants in Peru that were related to a variety of geographically distributed factors, including beliefs and customs as well as rugged geography with limited health system access [
32]. This was also seen in another study in Burkina Faso showing that children aged 16–36 months living in the Centre Nord, Nord, and Sud-Ouest regions were less likely to be fully vaccinated for their ages than children in other study regions [
36]. In our study, only one health district (Sindou) showed a clear downward trend, in contrast to the average trend. This may be an outlier due to its small sample size; there is no indication that this district has encountered any particular difficulties, especially since it is not located in an insecure area [
37]. Future research should aim to understand the reasons behind the observed heterogeneity between districts in vaccination coverage. Qualitative research can help identify local contextual factors that may influence vaccination uptake and inform the development of targeted interventions.
Burkina Faso generally has high vaccination coverage compared to other countries in the region, with DTP3 coverage reaching about 90% in infants aged 12–23 months in 2017 [
38,
39]; however, in the most recent DHS report, coverage ranged between 56 and 92% from region to region [
40]. Previous studies have identified several determinants of infant vaccination coverage in Burkina Faso, including region, distance from health centers, season of children’s birth, rurality, maternal education, and socioeconomic status [
36,
41,
42]. Regional disparities in timely vaccination coverage have also been observed, and it has been hypothesized that terrorist attacks are likely to increase these disparities [
36,
37].
As suggested by this study and others, the COVID-19 pandemic may also have reinforced existing inequities in vaccination in regards to locality of residence [
19,
22,
43,
44]. Arguably, the pandemic has further reduced access to healthcare services in rural and remote areas, whether by reducing door-to-door campaigns and outreach activities, making transport more difficult, causing stock-outs at primary healthcare centers, or increasing home deliveries [
45‐
47]. This heterogeneity highlights the importance of considering local context and variations in public health programs, as well as the local repercussions of natural or external events. To achieve high vaccination coverage rates and protect infants from preventable diseases, it is crucial to prioritize interventions and research efforts to target vulnerable populations who may have been disproportionately affected by the COVID-19 pandemic.
Our study conducted sensitivity analyses to examine the 2010–2021 trends in the proportion of children with age-appropriate full vaccination. The findings do not suggest steady trends, irrespective of the site or the type of vaccines. Coverage increased slightly when from 2010 to 2021, but not steadily; rather, there were upward and downward changes in between. Our trends contrast with those observed in the 2010 and 2021 DHS reports: When we concentrated on basic vaccines, our trends showed an increase in coverage in the Cascades (42.7% vs. 57.1%), Centre-Ouest (65% vs. 86.7%), and Nord regions (64.8% vs. 72.3%), while DHS reports showed heterogenous trends (66.3% vs. 92.9% for Cascades; 82.4% vs. 80.7% for Centre-Ouest; 96.8% vs. 77.4% for Nord) [
23,
40]. Poorly organized and inefficient systems, inadequate knowledge amongst health workers about vaccination, and challenges in recalling vaccination dates may have contributed to the decline [
48,
49]. The introduction of new vaccines into the Burkina Faso immunization schedule, the rising insecurity and the pandemic may also have played a role [
50,
51].
In terms of vaccine coverage, less variation was observed between basic vaccines and those added to the immunization calendar in 2013. The introduction of new vaccines, such as the rotavirus and pneumococcal vaccines, may have contributed to more variability in coverage compared to the basic vaccines. Although the number of vaccines included in the routine immunization calendar for children < 14 months increased from 9 to 15 between 2010 and 2015, the largest declines in vaccination coverage were observed after 2015. One possible reason for this is the challenges in ensuring consistent supply and delivery of these new vaccines after their introduction. Moreover, several countries in West Africa, including Burkina Faso, acquired vaccines from a different source due to global vaccine supply issues in early 2020 [
52]. This change, along with the emergence of the pandemic, may have played a role in the variability in vaccination coverage between basic vaccines and newer ones. According to the 2021 DHS report, 79% of children aged 12–23 months received all 8 doses of basic vaccines, while only 36% received all recommended vaccines (basic vaccines plus rotavirus and pneumococcal vaccines) according to the national immunization schedule [
40]. This gap between the actual and recommended vaccination coverage is consistent with our results and suggests a need for improvement in the implementation and delivery of vaccination services. Future efforts should include improving vaccine supply chain management and strengthening the capacity of immunization programs to ensure consistent and equitable vaccine access for all individuals.
Limitations
The biggest limitations of this study are its small sample size and the fact that it was a natural experiment and thus not determined by a power calculation; consequently, some of our estimates have wide confidence intervals. Secondly, our results may not be representative of all the children in the study area, since the analyses were limited to those infants who had a vaccination booklet available to be checked and recorded by surveyors. Excluding infants who did not have a vaccination booklet may have introduced errors in our study; however, sensitivity analyses performed to compare the characteristics of infants with and without vaccination booklets did not indicate any significant differences. This study cannot distinguish between vaccines routinely administered at health facilities and those provided during mass campaigns. Although COVID19 could have affected vaccination coverage through these two mechanisms, it is unlikely that the very brief interruption of mass campaigns could have had a significant impact on vaccination coverage, particularly among infants. Lastly, our study focused primarily on rural children and may not be generalizable to children living in urban areas, since studies have found significant differences in the effects of COVID-19 on vaccination coverage in different settings [
32,
36].
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