Vaccine hesitancy and the white whale
Understanding vaccination hesitancy on the turbulent waters of COVID-19
Whaling in North America during the mid-19th century was a fascinating, and truly barbaric, method of producing soap and lamp fuel. Sailors would routinely embark on three-year voyages for relatively little pay at great personal risk. Upon sighting a whale, all hands would launch the whaleboats, small vessels, each with ten or so sailors, to engage the fifty-ton sperm whale. The whaleboats were usually commanded by the first and second mates who were armed with lances and coordinated the chase. The fates of each sailor were intricately bound to one another. If the small boat were capsized or destroyed by the whale, all hands would likely be lost.
Mr. Starbuck, the fictional first mate of the Pequod from the American classic Moby Dick, addressed the crew at the beginning of the voyage with some clear-eyed words:
“I will have no man in my boat who is not afraid of a whale.”
Upon hearing these words, the story's narrator, Ishmael, offered his own reflection:
“By this he seemed to mean, not only that the most reliable and useful courage was that which arises from the fair estimation of the encountered peril, but that an utterly fearless man is a far more dangerous comrade than a coward.”
These passages linger in my thoughts as we enter, at the time of this writing, yet another period of severe COVID outbreaks, this time fueled by the highly contagious delta variant. Much like the 19th century whalers, teamwork is paramount, and we will all share in the eventual success or failure of our voyage.
At this point in the pandemic, we have significant tools to combat COVID. The mRNA vaccines have been shown to be highly effective at preventing hospitalization and death. Yet, in many parts of the U.S., vaccination levels remain low, primarily due to otherwise healthy individuals simply refusing to take one. This holds true even in areas where current COVID infection rates and hospitalizations are skyrocketing.
I think most of us would agree with Ishmael's interpretation of Mr. Starbuck's statement; rational decisions in the face of danger should follow a careful, and accurate, estimation of the encountered peril. This is fundamentally about how individuals evaluate risk and applies to COVID just as it does to whales. In a recent study, Trueblood et al. investigated how risk attitude relates to COVID vaccine intentions. They presented participants with a series of financial choices, asking participants whether they would prefer to receive $50 for certain or play a game where they would win $100 with probability p and win nothing with probability 1-p. The value of p was systematically varied to assess an individual’s degree of risk aversion. They found that individuals who reliably made risk averse choices, by consistently refusing the game and taking the certain $50, were more likely to report increased vaccine hesitancy.
I found these results to be a bit counter-intuitive at first. I obtained the vaccine as soon as I was eligible, being risk averse about the dangers of a potential COVID infection. On the other hand, delaying, or outright refusing, a COVID vaccine could be interpreted as risk averse behavior if one holds incorrect beliefs about the safety of the COVID vaccines and potential side effects. As described by Trueblood et al., turning down a vaccine in this context can be viewed as a type of omission bias, favoring inaction over taking an action, where such individuals may view potential side effects as more serious than the disease itself.
Let’s take this idea of risk a step farther. The financial gambles used in Trueblood et al. are a standard method of risk assessment and are defined using gains, i.e., winning (never losing) different sums of money. Using prospect theory as a guidepost, we know that individuals can be both risk averse for gains and risk seeking for losses. An individual is risk seeking for losses when they prefer a clearly inferior alternative on the basis that it carries with it the possibility, however slim, of avoiding any negative outcomes. A simple example would be preferring to play a coin-flip game where you win nothing on heads and lose $100 on tails versus simply losing $10 for certain. Clearly, you will do better, on average, by taking the small, sure loss, but the coin-flip game may look attractive if you are trying to avoid losing money at all costs.
The vaccination decision is ultimately one about potential losses, not gains. The best outcome is the status quo (person stays healthy), all other outcomes are clear losses (become sick from COVID and/or experience vaccine side effects). For some individuals, we may be able to describe their vaccine hesitancy as risk seeking for losses behavior. The decision to take a vaccine carries with it guaranteed exposure to a small amount of risk, because while both mRNA vaccines are very safe and extremely effective, some side effects may occur, which is true for any medication. To a vaccine hesitant person, taking a vaccine may feel like accepting a sure loss - a self-inflicted exposure to risk. Refusing the vaccine, in contrast, may appear analogous to a coin-flip game. Perhaps they haven't yet been infected by COVID, so by denying the vaccine they are clinging to a small probability of experiencing zero negative outcomes - either from COVID or by vaccine side effects.
Such risk seeking behavior is further exacerbated by misinformation about the severity of COVID and false claims about vaccine side effects. While major social media websites are actively removing such content, there is evidence that this may be a losing battle. Complacency may also be major factor in this regard. In an editorial published in Nature Medicine, Machingaidze and Wiysonge suggest that individuals from high-income countries who do not routinely experience the devastating effects of serious contagious diseases may have higher complacency than those from lower-income countries. Someone who has never seen a whale up close may not fully appreciate the threat it poses.
We can elaborate a bit more on potential outcomes. The negative outcomes involved in a vaccine decision are not identical for everyone. For individuals with good job security, the negative outcomes are primarily health related. For others, time lost at work to recover from the vaccine could be financially catastrophic. A recent poll by the Kaiser Family Foundation found that time lost at work due to side effects were a major factor in vaccine hesitancy, especially among Black and Hispanic workers. It is also worth noting that while the vaccine is free, subsequent healthcare is not. These additional factors may induce some individuals to keep chasing risk by avoiding the vaccine.
If the end of the global pandemic were in sight, we could view the vaccination decision as a choice that is only presented once. But, as described by Ed Yong in a recent article published in The Atlantic, COVID is likely to become endemic, meaning that, akin to the common cold, it will always be present. I think this has the potential to change how some individuals view vaccine decisions. I can understand an individual playing the risky coin-flip game once to avoid the sure loss of $10. If forced to make the same choice a hundred times in a row, it is harder to understand why someone would consistently select the coin-flip game over taking a series of small, sure losses. An endemic virus changes the risk calculus by removing the small, already vanishing, probability of avoiding exposure to COVID.
It's not enough to remove all disinformation from Facebook and provide accurate information to individuals on the merits of collective immunity. We need to better understand how people who refuse vaccines evaluate the various risks. I’m convinced that a better understanding of relevant decision processes has the potential to improve current vaccination efforts, which is desperately needed, given the current strain on U.S. hospitals. The Trueblood et al. study found that risk attitudes also explained differences in how receptive individuals were to different media vaccine messaging. Further work along these lines may be useful for "nudging" individuals to take up the vaccines.
The sailors on the Pequod learned the hard way that whales are not to be trifled with. We need everyone on board to better evaluate risks, as COVID is putting us all in danger.
-Clintin P. Davis-Stober, Ph.D.