The spread of vaccine-preventable disease around the globe threatens decades of public health progress and puts millions of people in danger.
The global problem is illustrated by the decline in vaccination coverage. The Advisory Committee on Immunisation Practices has recommended 15 potentially severe illnesses for children under 24 months of age. These vaccination rates have decreased.
Canada is not immune to this epidemic. As at July 19, there were 4,206 cases of measles (3,878 confirmed and 328 probable). In 2025, 10 jurisdictions will report this number (Alberta British Columbia Manitoba New Brunswick Northwest Territories Nova Scotia Ontario Prince Edward Island Quebec Saskatchewan).
The decline in vaccination coverage can be attributed to misleading or deceptive. We used operations research to better understand vaccine hesitancy. We explore anti-vaccination attitudes and sentiments through an integrated study that combines insights from psychological reactions with eHealth literacy.
What fuels the skepticism towards vaccines? There are a variety of factors, including personal, social and environment-related ones.
How we make decisions (and how often they are wrong)
Heuristics are commonly used by people to simplify complicated issues.
This can lead to a sacrifice of accuracy in the name of efficiency. Cognitive biases are distortions that affect judgment and decisions.
These processes influence vaccination decisions in the same manner as they do any other.
Read on: How cognitive prejudices and adverse reactions influence vaccine decisions, including your own.
Skepticism towards vaccines is often associated with concerns about possible side effects. These fears are fueled by our tendency to overestimate the negative effects, also known as risk perception bias.
The Nature Scientific Reports has published a study that confirms vaccine-hesitant people are more sensitive to risks and overestimate the potential side effects.
In a study published in the journal Vaccine: X on cognitive biases associated with vaccine hesitancy, four factors were found to be significantly related. These include:
- Fear of side effects (skepticism)
- Carelessness about the risks associated with not getting vaccinated.
- Optimistic attitude: believing that they are less likely to get sick (optimistic bias)
- Naturalness bias factor: Preference for natural products
Existing beliefs may also have a significant impact on evaluations and decisions. People are more likely to seek out information that confirms or reinforces their existing convictions. Confirmation Bias affects the rational evaluation and assessment of vaccine safety and efficacy.
This bias is particularly important when it comes to determining how susceptible people are to false information, which can be a major obstacle to vaccination uptake.
The Myth of Rationality
It is useful to assume that humans can make rational decisions when developing simulations or models. This includes those used in game theory. Game Theory can be used to analyze phenomena that arise from the interaction between multiple decision makers. It allows us to predict possible scenarios.
The insights from behavioral economics, and cognitive psychology show that any assumption about rationality can be wildly optimistic.
” Bound rationality” is a description of the limitations within which reason works. The limitations of human judgments are limited by a lack of information, our limited analytical abilities and time constraints.
Even the most convincing information will not convince everyone who is hesitant to get vaccinated. It can sometimes have the reverse effect.
Understanding the psychological and attitude predictors for vaccine hesitancy will allow us to compare their impact in various contexts. Contexts are the environment (or setting) that influences the decision of individuals about vaccines.
The comparisons reveal that the thought patterns that lead to vaccine hesitancy are modifiable, as opposed to stable risk factors such as demographic factors like unemployment, low education, younger age and rural residence, or status like sex, migration and status .
Changes in vaccination decisions over time
Social dynamics influence the evolution of vaccination behaviours over time. Researchers studied to understand why some voluntary vaccination programs fail. They found that self-interested decisions lead to lower vaccination rates, and can prevent the complete eradication from illnesses that vaccination would otherwise be able control.
The study presented two scenarios based on the assumption that parents are perfectly rational in their decisions.
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They accept that there may be side effects, but they still want to protect their child.
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They can save money by not vaccinating their children, while hoping that they won’t get the disease.
Researchers found that when parents make these choices, vaccination rates drop, especially in cases of highly contagious disease.
A second study examined why vaccination rates fluctuate wildly over time, instead of staying steady.
The authors examined how people mimic each other and two real vaccine scares in England and Wales. One occurred in the 1970s when the whooping-cough vaccine was introduced and the second in the 1990s, with the MMR vaccine.
Parents vaccinated and did not vaccinate as they followed herds in the direction that seemed the safest. This led to boom and bust cycles, and an unstable protection of the community from targeted diseases.
This can lead to localized pockets of low vaccination, which benefit those who are not protected through herd immunity. However, unvaccinated clusters may also become high-risk groups if the protection decreases.
Social media echo chambers
The COVID-19 epidemic has shown how misinformation, disinformation and information voids can damage public healthcare. This includes immunization coverage, and vaccination hesitancy.
Two factors can help us understand the relationship between misinformation spread on social media and vaccine hesitancy: the amount of exposure and how convincing social media is.
During the COVID-19 epidemic, the social media content that was vaccine-skeptical had a negative impact and fueled doubts about the safety and effectiveness of vaccines, especially when it wasn’t flagged by fact-checkers.
Unflagged misinformation was estimated to have a 46-times greater impact on vaccine hesitancy than content that had been flagged.
Content that is factually accurate, but could be misleading — like a rare case where a young and healthy person died shortly after receiving a vaccine — can also play a crucial role in causing vaccine hesitancy.
Our own research and that of our collaborators argues that examining the role of social networks can help develop new strategies for promoting and increasing evidence-based vaccination literacy.
Elkafi Hassini was awarded Discovery and Alliance Grants funding by the Natural Sciences and Engineering Research Council of Canada to support this research.
Emanuele Blasioli has not disclosed any relevant affiliations other than their academic appointment.
