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Posted on October 6, 2021 at 5:00 AM

By  Govind Persad, JD, PhD

The United States, after wasting over 15 million doses since March and with a stockpile of 150 million more in freezers, reportedly ordered 200 million more vaccines from Pfizer/BioNTech for delivery starting in October. These orders may be motivated by the expectation of broad access to “booster” vaccines in the United States.

The World Health Organization and many ethicists have criticized the broad provision of boosters on the basis that they exacerbate global vaccine scarcity. But other influential commentators defend using hundreds of millions of doses as domestic boosters by claiming that “the approximately 100 million doses needed to boost high-risk Americans will barely make a dent in the several billion doses needed to vaccinate the world.”

Whatever one’s views on boosters, the “barely make a dent” argument reflects an indefensible cognitive bias. Vaccines save lives. The U.S. vaccine campaign is estimated to have prevented 279,000 deaths and 1.25 million hospitalizations between December 2020 and June 2021, while administering around 300 million vaccines. This suggests that 100 million extra vaccines would be expected to save just under 100,000 lives, and avert around 400,000 hospitalizations, which may count for even more in countries with less hospital capacity. Even if we make unjustifiably pessimistic assumptions about other countries’ capacity to use vaccines—say they waste half of what they receive—these doses would still save tens of thousands of lives and prevent hundreds of thousands of hospitalizations. 

Meanwhile, continued high efficacy of the two-dose series against death and hospitalization demonstrates that using those 100 million vaccines for boosters will have far less benefit. Using vaccines to save many thousands of lives and protect even more people from hospitalization doesn’t count for less just because we psychologically lump those good outcomes with millions of deaths and hospitalizations due to continuing global vaccine scarcity. Rather than arguing that boosters “barely make a dent,” those who defend buying millions of newly produced vaccines for boosters should admit that they prioritize reducing mild to moderate infections at home over saving lives and preventing hospitalizations elsewhere.

“Those who defend buying vaccines for boosters should admit that they prioritize reducing mild to moderate infections at home over saving lives and preventing hospitalizations elsewhere.”

Why might we feel like an extra million vaccines, or even 100 million vaccines don’t matter if many more people won’t be able to access vaccines no matter what we do? The psychologist Paul Slovic calls this phenomenon “pseudoinefficacy,” “the false belief that helping one person out of many doesn’t matter….When we become aware of all the people we aren’t helping, our actions feel like a mere drop in the bucket and we lose the motivation to act.” Other psychologists call this or related phenomena “proportion dominance,” “psychic numbing,” or even just the “drop-in-the-bucket effect.” 

Understanding how drop-in-the-bucket thinking leads us astray is a first step. But how can we reduce the effects of this cognitive bias? Some suggest that encouraging more careful deliberation, minimizing the emphasis on the number of people in need, or highlighting the benefits to those who are helped could be effective. But more research on blunting the power of drop-in-the-bucket biases could be crucial to saving lives and accelerating vaccination worldwide.

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