Fear may be the biggest thing that’s keeping the coronavirus pandemic from going away for good, a new study reveals. Researchers from New York University say the way the public reacts to fear — both positively and negatively — continues to fuel the multiple waves of COVID-19 over the last two years.

In a new mathematical model, study authors show how public fear is leading to behaviors that are both curbing the spread of COVID and spreading it further.

“Emotions like fear can override rational behavior and prompt unconstructive behavioral change,” says Joshua Epstein, professor of epidemiology at NYU School of Global Public Health, in a university release. “Fear of a contagious disease can shift how susceptible individuals behave; they may take action to protect themselves, but abandon those actions prematurely as fear decays.”

The ‘Triple Contagion’

In NYU’s “Triple Contagion” model of disease, fear, and behavior, researchers illustrated how acts like social distancing suppress the pandemic, but things such as vaccine denial causes COVID cases to spike again. Traditionally, the team says epidemic models ignore the human element and the fears that drive behavior.

In the new study, researchers say fear of catching the SARS-CoV-2 virus caused many people to self-isolate and wear face masks. This led to the first drop in cases in 2020. However, with the virus subsiding, fear tends to evaporate as well, leading to more people leaving isolation and discarding their masks. This leads to a new wave in the pandemic as more people start interacting with infected patients.

Study authors are seeing the same cycle with the coronavirus vaccine. Fear initially motivated millions of people to get the vaccine in the spring of 2021. However, as fear of infection goes down and misinformation about vaccines continues to spread, vaccination rates are dropping. Now, COVID-19 is re-emerging again as the Delta variant takes over.

“If fear of COVID-19 exceeds fear of the vaccine, it may spur vaccination and therefore suppress the virus, a trend we saw in the U.S. this spring as millions of Americans were vaccinated and cases dropped,” Epstein explains.

“But if people think the vaccine is scarier than the disease—whether they are skeptical about how serious COVID-19 is or because of baseless fears of the vaccine fueled by misinformation—our model shows that people avoid vaccines and a new disease cycle can grow. We’re seeing this play out in real time in regions with lower rates of vaccination, where the Delta variant is rapidly spreading and cases are surging.”

‘Fear Itself Can Be Contagious’
The new model Epstein’s team created also accounts for behavioral factors, like the percentage of the population that fears a disease or vaccine and how vaccine side-effects generate more fear. It combines these factors with standard epidemic measures such as disease transmission and vaccination rates.

Researchers add that they also recognize that fear is not a set number; it grows and spreads due to misinformation and fear-based news reports, but fades when more reassuring news arrives.

“Neuroscience suggests that fear itself can be contagious, but fear also tends to fade or decay. In our model, people may overcome their fears of disease and vaccine—either over time, when disease prevalence drops, or from interactions with others who recovered from COVID or got the vaccine and had minimal side effects,” Epstein says.

“Our ‘Triple Contagion’ model draws on the neuroscience of fear learning, extinction, and transmission to reveal new mechanisms for multiple pandemic waves of the sort we see in the current SARS-CoV-2 pandemic and novel ways to think about mitigating its spread,” adds Erez Hatna, clinical associate professor of epidemiology at NYU School of Global Public Health.