Perceived risk and vaccine hesitancy: Quasi-experimental evidence from Italy

In March 2021, Italian health authorities suspended the Vaxzevria vaccine (VA) for 4 days over reports of very rare blood disorders among recipients. We exploit the quasi-experimental setting arising from this break to study the drivers of vaccine hesitancy. Before the suspension, the VA vaccination trend followed the same pattern as Pfizer-Biontech (PB). After the suspension, VA and PB injections started to diverge, with VA daily decreasing by almost 60 doses per 100,000 inhabitants for the following 3 weeks. The resulting vaccination rate was 60 percent lower than the value that would have stemmed from the VA pre-suspension pattern. We show that the slowdown was weaker and less persistent in regions with higher COVID penetration and steadier and more pronounced in regions displaying greater attention to vaccine side effects as detected through Google searches. The public's interest in vaccine adverse events negatively correlates with COVID cases and deaths across regions.