Santos 2021.

Study characteristics
Methods	Study design: randomised controlled experiments Type of publication: research letter Setting and dates:large Pennsylvania health system, December 2020 to January 2021 Country: USA Language: English
Interventions	Intervention:  Email, that framed the decision to be vaccinated by noting that many US residents and fellow employees had chosen to be vaccinated, i.e. social norms, Email reframing risks of COVID‐19 vaccine as small Delayed control: email received 3 days later
Population	Population: healthcare workers Age: 18 and older Gender: NR Ethnicity: NR Number of participants (recruited/allocated/evaluated): 9273 Inclusion criteria: Employees of the Geisinger Health System, who had not scheduled a COVID‐19 vaccination
Outcomes	Primary outcome:  Percentage of participants registered on the vaccination scheduling portal Secondary outcomes: Number of employees who opened emails after 3 days  Number of employees who clicked scheduling links after 3 days
Notes	Funding: NR COI: None