There is no doubt that the Covid-19 vaccines are protecting people from death and illness. Yet a significant number of people (an estimated 93 million) are still reluctant (or delaying) to get the shots. Vaccine hesitancy poses a public health threat for herd immunity.
There are several cognitive biases (errors in judgment) behind any vaccination decisions that need to be addressed. These cognitive biases are extremely common in most medical decision-making (Kahneman, 2011).
1. Vaccine distrust
Some people will not accept any vaccines at all. They worry about safety and unknown side effects. Moreover, most Americans are suspicious of big pharmaceutical companies that have developed the shots. They tend to believe that these companies do not have the public’s best interest in mind.
2. Risk perception
Some people are deeply skeptical about the dangers the virus poses. They may not accept a COVID vaccine because, to them, the risks of the vaccine seem greater than the risks of getting seriously ill. They may also adopt an overly optimistic view about themselves and the likelihood of experiencing negative events. Unrealistic optimism can have significant health consequences, as shown by a recent increase of infections among unvaccinated folks. However, once they become ill, the risk perception changes. They trust their own experiences more than science.
3. My body, my choice
Vaccination is considered a public good, like national defense or street lighting. The decision to vaccinate is not a personal choice. Individual decisions have collective consequences. The nature of transmission via person-to-person proximity poses risk to others. The negative externalities are the main reasons for the vaccination push by the federal government or local jurisdictions. So, framing vaccines in their impact on others in one’s family or community could motivate people to vaccinate.
4. Confirmation bias
Belief beats out fact. People tend to embrace information that supports their beliefs and reject information that contradicts them. For example, a person who is already skeptical about vaccine safety would most likely search for information confirming this belief. Confirmation bias makes it difficult for new information (the relative risks of vaccination versus the disease) to penetrate existing beliefs.
5. Availability bias
People assess an event’s likelihood by how easily specific outcomes come to mind. For example, a risk that is familiar (vaccine being unsafe) will be seen as more serious than the risk of disease itself. Media and social circles are much more likely to focus on these rare occurrences, so an individual can easily recall them. Biased assessments of risk can negatively influence how we respond to health risks.
6. The illusion of causality
The illusory causality is a belief that there is a causal relationship between two events that are actually unrelated. We humans generally aren’t great at reasoning objectively about uncertainty as we go about our daily lives. Our intuitive mind extracts causality from coincidences. For example, people may decline immunizations due to false claims that vaccines could alter people’s genes, cause cancers, and infertility. These beliefs lead people to use any incidence of vaccine side effects to confirm their bias.
In sum, cognitive biases can undermine how the general public makes sense of scientific data and present potential barriers to optimal decision-making. No human population is immune to cognitive biases. These biases may be intensified by the current climate of uncertainty and public mistrust.