Default change nudges Covid-19 vaccine uptake: a randomized controlled trial

Abstract

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.

Waste Not Want Not: Computational Methods to Maximise Attendance in Group Research

“…Given the observations made in the exploratory analysis of Experiment 2, it seems highly plausible that participants opting out of timeslots is much preferable to participants opting in to timeslots. In other words, for the purpose of allocation ease it would likely prove fruitful to assume that participants are able to partake in all slots while giving them the opportunity to opt out of unsuitable ones, rather than asking them to select which ones are suitable (Tentori et al, 2022;Yan & Yates, 2019).…”

Public policy and conspiracies: The case of mandates

“…Research has shown that setting up an appointment unannounced increases uptake even though people can opt out of the appointment. This nudging intervention has been shown to be successful for influenza shots [ 9 ] as well as COVID-19 [ 48 ]. The latter study found a 32% relative increase of vaccination uptake (3% in absolute terms) through scheduling an appointment unannounced.…”

Solving Last-Mile Delivery Challenges is Critical to Increase COVID-19 Vaccine Uptake: A Cluster Randomized Controlled Trial

“…Lang et al, 2022;Milkman, Gandhi, Ellis, et al, 2022) produced very small or negative effects. Text-based reminders in the U.S. (Dai et al, 2021;Rabb et al, 2022) and defaulting people into a vaccination appointment in Italy (so that they are forced to opt out, see Tentori et al, 2021) increase vaccination rates between 0 and 3.5 percentage points. Notes: This table reports the intervention types, locations, vaccines administered, and effect sizes in percentage points for RCTs testing interventions used to increase the uptake of vaccines.…”