By Ella Heckman, C2ST Intern, Loyola University

Vaccines are tools of modern medicine used in keeping us safe and healthy from the spread of disease. The science of vaccination has come a long way in the last 200 years since the first vaccine, the smallpox vaccine, was developed in 1796. As science has developed, so too has the role of the public in deciding whether or not to get vaccinated against preventable diseases. This includes you, too! The amount of information available to us in making these decisions can be overwhelming, especially if we don’t understand the science. 

Anxiety, misunderstanding, and misinformation around vaccines can lead some people to forgo vaccines entirely, leaving them vulnerable to preventable disease. It’s ok for you to feel any level of uncertainty or anxiety about your health and the health of your loved ones. This phenomena is known as “vaccine hesitancy” and is resulting in more and more people across the world not getting vaccinated. We can feel empowered to make decisions about our health by making evidence-based choices, being aware of cognitive biases, and understanding risk.

What is risk and how do we communicate it?

We are not always rational creatures, we often make decisions based on our emotions or on incomplete information. While it can be scary to think that the things we choose to consume or the vaccines we get have a non-zero chance of causing a bad reaction, that doesn’t mean that the risk of that bad reaction happening to us is high. The complete absence of risk cannot be scientifically demonstrated making communicating risk one of the great challenges in reducing vaccine hesitancy.

For example, Human Papillomavirus (HPV) is the most commonly sexually transmitted infection in the world, affecting 80-90% of women and men over their lifetimes. HPV is strongly associated with cervical cancer in women and oropharyngeal cancer in men. Fortunately, high-risk HPV infections can be prevented with effective and safe vaccine regimens and have been in regular use around the globe for the last decade. 

However, in 2013 Japan’s government announced a ‘temporary suspension’ of its recommendation for the HPV vaccination. This was a result of the spread of misinformation and allegations of adverse risks posed by the vaccine in the media and on social media in Japan. The suspension of official recommendation lasted until 2022, leaving almost an entire generation of girls unvaccinated against HPV in Japan. Following the suspension, HPV vaccination rates dropped from 70% to almost zero despite the HPV vaccine still being offered for free. According to current data, abnormal cytology in cervical cancer screenings for the non-vaccinated generation of women born in 2000 is significantly higher than that of the previously vaccinated generation, and will account for 900 deaths and 3700 incidences for this age group alone. 

Although the likelihood of adverse effects are extremely low, our feelings of anxiety and level of misunderstanding are not. 

Because scientific assessments typically operate on margins, probabilities, and percentages, rather than saying definitively that there is no risk, it can be difficult for us to understand the reality of their exposure to risk. As in the HPV case, reports of side effects were covered extensively in the media, although the actual chances of having side effects related to the vaccine were extremely low. 

Uncertainty is inherent to communicating risk, but uncertainty is not always something to be afraid of. Although the chances of something bad happening can be extremely rare, that doesn’t mean scientists can tell people what will happen every time, 100% of the time. The spectrum of risk, if not communicated clearly, can become an outsized potential danger to people. This is what has happened in Japan with the HPV vaccine. Instead, if we think about risk in a larger framework of risk-benefit we can more appropriately make decisions based on the evidence, rather than perceived danger. 

How we assess, manage, and communicate risk are all important – related but distinct aspects of risk. For example, in the case of HPV vaccines, cancer prevention is the long-term benefit. In contrast to this, fears of adverse effects are immediate and can make our sense of perceived danger feel larger. The CDC puts it simply, “Getting vaccinated is safer than getting sick.” These are discussions to be had with a healthcare provider, someone you can ask questions of who can answer them with clarity, consistency, facts, and openness. 

How do our brain’s patterns impact vaccine hesitancy?

We live in an age of social media, of constant stimulation and constant information. We are also human, which means our brains take shortcuts sometimes to make the world around us easier to understand. These are mental heuristics. They are a type of cognitive bias, or a strong view that we already have about someone or something, based on what we think we know. 

Although these ways of thinking can be useful shorthand, they can also make it harder when trying to make evidence-based decisions and think critically when we receive new information. A simple example of bias related to vaccines is confirmation bias. If someone is already vaccine hesitant and hears on social media that the HPV vaccine causes neurological effects, they are more likely to believe that because they are already nervous about it. There are other, more complex and interacting types of biases that impact our decision making. Being aware that we are not always rational creatures who can assess evidence presented to us fairly goes a long way in helping us try and make more fact-based decisions. 

At the end of the day, we all want to be making decisions that are based on evidence and are grounded in reality. By better understanding the inherent nature of risk and uncertainty in science, and in life, we are more adaptable and better able to process new information as it is presented to us. This is especially relevant as we navigate important health decisions for ourselves, our loved ones, and for the good of our communities.