Quasi experimental study of SMS text messages as a nudging strategy for Covid-19 vaccination in Sweden

Abstract

Introduction In the roll-out of the COVID-19 vaccination program, a variety of policy tools were used to increase vaccination rates in Sweden. A SMS nudge intervention was implemented to increase vaccine adoption in Värmland and Västra Götaland among residents aged 16–39, 12 weeks after those aged >18 became eligible for vaccination in those counties. Aim The purpose of this paper is to assess the effect of SMS nudge interventions on COVID-19 vaccination uptake in Sweden. Method To analyze the adoption of the COVID-19 vaccine, quasi-experimental evidence and differences-in difference methodologies were utilized. The period of interest is from week 26 to week 44 of 2021 (6 weeks after the SMS reminder). The targeted age group was divided into three strata for in-depth evaluation. The robustness of the model was examined by incorporating county-specific covariates and analyzing multiple timeframes. Results The estimated effect of the SMS nudge on COVID-19 vaccination uptake was a 0.0083 percentage point decrease in vaccination rates, with very wide confidence interval (95% CI -0.06; +0.05) 30-39- year-olds demonstrate a small positive impact in the treated group with a value of 0.005, while 16-17 and 18-29-year-olds are estimated at -0.04 and -0.01 units, respectively. Conclusion This thesis finds no evidence that SMS nudging has increased vaccination rates for COVID-19 in Sweden. Thus, instead of SMS, policy makers could consider utilizing other nudges. This result contradicts with previous studies, most likely because of the time lapse between the eligibility contact and SMS nudge implementation.