Vaccine hesitancy is described by SAGE as a “delay in acceptance or refusal of vaccines despite availability of vaccination services”. It might also be considered a “state of indecision and uncertainty that precedes a decision to become (or not become) vaccinated”. In 2019 the WHO included vaccine hesitancy as one of the ten threats to global health. A variety of factors influence this hesitancy, categorised into ‘the 5C model’.

Confidence – trust in…

  • The effectiveness and safety of vaccines
  • The system that delivers them
  • The motivations of policymakers who decide on the need of vaccines


  • Perceived risks are low, and vaccination is not deemed a necessary preventative action

Constraints (an alternative to convenience)

  • Physical availability
  • Affordability and willingness to pay
  • Geographical accessibility
  • Ability to understand – language and health literacy
  • Appeal of immunisation service


  • Individuals’ engagement in extensive information searching
  • The more information a person seeks the more vaccine-critical sources will be obtained

Collective responsibility

  • Willingness to protect others through herd immunity


Vaccine hesitancy is by no means a recent phenomenon, growing in line with increasing access to information through social platforms and the expansion of vaccine portfolios. Numerous studies on the role of the internet in influencing vaccine sensibilities have concluded that it represents a threat to informed decisions about vaccination. This encyclopaedic store of information includes swathes of misinformation, intentional or not.

The term ‘infodemic’ is pertinent to this problem; understood to mean a surplus of information that includes misinformation, we can suggest that an ‘infodemic’ exacerbates vaccine hesitancy by challenging acceptance of scientific fact. This poses a huge risk to general public health, particularly in times of pandemic. Tackling vaccine hesitancy is a feat that requires an understanding of the causes as well as an answer to each of them.

Addressing colleagues at the World Vaccine Congress in 2022 Dr Nicole Lurie, suggested that they were “still not really understanding” the “human behaviour” of vaccine hesitancy.* Perhaps, to people so comfortable and familiar with the intricacies of vaccine safety and efficacy, some of the reasons above are incomprehensible. So how can we better understand and address this “behaviour” in order to make progress out of the pandemic? We explore this in our article on overcoming vaccine hesitancy.

*To see Dr Nicole Lurie in action at the World Vaccine Congress in Washington, April 2023, click here.