Taking Stock of Global Immunisation Coverage Progress: The Gains, the Losses and the Journey Ahead

"Building trust...can be achieved by providing access to reliable information and promoting discussion about the benefits and side effects of vaccines that can address the concerns of parents, caregivers and the general public in a respectful and culturally sensitive manner."

Despite substantial gains made in improving immunisation coverage at the global level, there remain supply- and demand-side challenges with reaching and sustaining optimal coverage. This is the starting point for a commentary that stresses the need for targeted, context-appropriate strategies for reversing problematic aspects of current trends.

A closer look at the data in the July 2019 update of the World Health Organization (WHO) and United Nations Children's Fund (UNICEF) Estimates of National Immunization Coverage (WUENIC) reveals that the incremental changes in immunisation coverage are of larger magnitude in low- and middle-income countries (LMICs - most of which started from very low levels of coverage) compared with high-income countries (HICs). While immunisation coverage remains suboptimal in many LMICs (particularly in Africa and South East Asia) despite achieving substantial increases in coverage, there have been relatively marginal gains or even declines in several HICs (especially in Europe and the Americas). Although these regional trends may mask disparities between and within countries, they imply that millions of children around the world are still missing out on lifesaving vaccines in many part of the world. Recurrent outbreaks of vaccine-preventable diseases, such as yellow fever and measles in many LMICs, as well as re-emerging measles epidemics in Europe and the United States, are an indication that immunisation coverage gains are yet to reach optimal levels across countries and regions.

Supply-side challenges encompass immunisation programme factors such as vaccine procurement, cold chain and logistics management, service delivery, and vaccine information systems. Vaccine supply is also hampered by broader health systems factors such as gaps in: immunisation policy, standards, and guidelines; governance and management; human resource availability; and sustainable financing.

Among the approaches to such challenges: the deployment of improved supply, inventory, and stock management information systems to monitor vaccine stock levels in real time, and the crowdsourcing of reports of stockouts from patients and community volunteers that are then sent to relevant health system entities for improved vaccine availability.

Demand-side factors include perception of the low incidence and risk of vaccine-preventable diseases, unfounded fears of vaccine adverse effects, and misperceptions - all of which fuel anti-vaccine sentiments. In high-income countries (HICs) in particular, the validity of science and the legitimacy of medical authority are increasingly being scrutinised, with more individuals questioning the relevance of vaccination in the context of consumerism. Furthermore, due to time constraints, limited resources, inadequate information, and insufficient training, frontline health personnel may have limited capacity and confidence to deal with emerging vaccine-related concerns and to clearly communicate vaccine benefits and risks.

Vaccine-hesitant individuals are a heterogeneous group of people with varying levels of concerns, doubts and perceptions about specific vaccines or vaccination in general. Thus, interventions that employ multicomponent strategies that are tailored, context-appropriate, and evidence-based appear to hold promise for addressing demand-side challenges. For instance, communication strategies using well-targeted dissemination of appropriate information and risk communication, such as about potential side effects and how to manage them, and appropriate community engagement, especially during immunisation campaigns, to allay fears and misperceptions. In addition, the commentary suggests a need for real-time surveillance and monitoring frameworks to promptly detect and respond to vaccine-related events, social media misinformation, and emerging concerns. "Information technology tools might play a role in this through timely and appropriate public education and strategic information sharing....It is also vital to continue involving key stakeholders, such as religious leaders, civil society organisations and immunisation champions in disseminating evidence-based messages on vaccines..."

In conclusion, "broad-based, context-specific strategies are needed to optimise access to immunisation services. Such strategies will have to address the various root causes of suboptimal vaccine financing, supply and availability, as well as demand-side barriers like vaccine hesitancy, while also instituting pre-emptive measures against the emergence of these problems in contexts where they are less prevalent. In addition to advancing the gains of vaccines in LMICs, global and national health systems have a collective responsibility to ensure the gains already made in high-income settings are not reversed. This is important for guaranteeing that the full benefits of immunisation are extended to all people, regardless of where they are born, who they are or where they live."