Volatility of vaccine confidence

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March 26, 2021

Last week, the European Medicines Agency declared the AstraZeneca COVID-19 vaccine safe and effective, after several European Union member states had suspended its use because of blood clot concerns. Will the public trust this message? This week's news could help—a U.S. phase 3 clinical trial of the vaccine shows promising efficacy in preventing symptomatic COVID-19. But sentiments toward vaccines are volatile and reflect external events—such as recent concern about AstraZeneca's efficacy data—as well as internal emotions.

Various polls on vaccine willingness made early predictions of low vaccine uptake owing to vaccine hesitancy. But with the ups and downs of virus surges, and more information—and misinformation—around the vaccines, confidence levels also had ups and downs. Vaccine willingness started to climb with news of an effective Pfizer vaccine, a second wave of infection, the emergence of new variants, and more lockdowns. Now, a reported safety risk and consequent anxieties have sent sentiments plummeting in some countries.

Author and physician Danielle Ofri called this undulation of sentiment “emotional epidemiology” as she reflected on the seeming eagerness, then hesitation or refusal, to receive the H1N1 influenza virus vaccine during the 2009 pandemic. COVID-19 is affecting the world at a much larger scale than H1N1; thus, vaccine hesitancy could pose a major threat to controlling the pandemic.

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