Vaccine Hesitancy: Understanding Better to Address Better

Success in vaccination programmes is dependent on a high vaccination coverage rate, yet the waning of public confidence in vaccines worldwide is a major challenge for public health experts. With a view to supporting efforts to address the complex and context-specific issue of vaccine hesitancy (VH), this paper describes the concept - noting that the renewed and growing interest in VH has led to the development of different tools and strategies, including some social marketing principles and practices, that can help to enhance vaccination acceptance.

According to the World Health Organization (WHO)'s Strategic Advisory Group of Experts (SAGE) Working Group on Vaccine Hesitancy, VH refers to delay in acceptance or refusal of vaccines despite availability of vaccine services. VH exists along a continuum from accepting all vaccines to, one other extreme, refusing all. VH is influenced by factors such as complacency, convenience, and confidence. Vaccine complacency is known to be present where the risk of vaccine-preventable diseases (VPDs) is perceived to be low, and where vaccination is not considered essential. It has been observed that VH is heavily impacted by lack of confidence in the vaccine's safety and efficacy as well as fears regarding the reliability and competence of the health system. In addition, the quality of vaccination services and their convenience (e.g., physical availability, geographical accessibility, and affordability) are factors that impact the decision of whether or not to be vaccinated. Furthermore, research has shown that vaccination decision-making should be studied and understood in a broader socio-cultural context; it is highly influenced by various factors such past experiences with health services, family histories, feelings of control, and conversations with friends.

The factors influencing VH can be explained on the basis of the epidemiological triad - i.e., the complex interaction of environmental (external) factors, agent factors (vaccine), and the host (parents). The determinants of VH are numerous and context specific and are presented separately in the paper, though they are interrelated.

• Environmental/external factors - Discussed here: the patient-health professional relationship; school immunisation requirements; social norms/collective values; vaccine policies and public health; and communication (e.g., via the internet) and the media, which "plays a significant role in vaccine uptake and influences the community both positively and negatively."
• Agent/vaccine specific factors - Discussed here: vaccine efficacy perception; vaccine safety perception; and disease susceptibility perception.
• Host/parental specific factors - Discussed here: race, education and income; and parents' decision, knowledge, and past experiences.

In terms of the way forward, "[m]any experts are of the view that its best to counter vaccine hesitancy at the population level and it can be done by including transparency in policy-making decisions regarding immunization programs, providing updated information to the public and health providers about the rigorous process undertaken before the introduction of new vaccines for the general population and diversified post-marketing surveillance of vaccine-related events. In addition, a special focus should be placed on listening to concerns and understanding the perceptions of the public to inform risk communication and to incorporate public perspectives in planning vaccine policies and programs."

Specifically, to counter VH, programme managers need to start by identifying the intended population and understanding the true nature of their particular vaccine and/or vaccination concerns. Causes of VH vary from country to country; hence, there is a need to identify locally relevant and context-specific causal factors before intervention strategies to address them can be planned effectively. "Finally, due to their critical role in sustaining the success of vaccination programs, there is an urgent need to undertake further research so as to understand why some health professionals, trained in medical sciences, still have doubts regarding the safety and effectiveness of vaccination."