Default change nudges Covid-19 vaccine uptake: a randomized controlled trial
Although vaccination against SARS-CoV-2 is considered the central strategy against the pandemic, uptake lags behind target rates. To explore whether this rate could be enhanced by a nudging strategy that exploits the status quo bias, we conducted a randomized controlled study in northern Italy comparing vaccination acceptance among 2,000 adults aged 50-59 who were either invited to set an appointment (opt-in group) or assigned an individual appointment (opt-out group). Results indicate an increase in vaccination rate for the opt-out group compared to the opt-in group of 3.2 percentage points — a 32% relative increase. This suggests that a significant portion of those who remain unvaccinated may not hold strong beliefs against vaccination, but rather tend to inaction and may therefore be nudged toward vaccination with a reduction of action required.