# Using the Diffusion of Innovation Theory to Understand COVID-19 Booster Hesitancy in Adults

## TL;DR

This study explores why many vaccinated adults in the U.S. are hesitant to get a COVID-19 booster vaccine, using a theory about how new ideas spread.

## Contribution

The study applies diffusion of innovation theory to understand booster vaccine hesitancy and identifies group-specific barriers.

## Key findings

- Booster hesitancy is linked to low vaccine literacy and high institutional mistrust, especially in laggard and refuser groups.
- Perceived risk of future infection and information needs vary significantly across adopter groups.
- Messaging should be tailored to address the unique concerns of different adopter groups to improve booster uptake.

## Abstract

Public health relevance—How does this work relate to a public health issue?
COVID-19 continues to be a significant public health issue, related to both morbidity and mortality because of waning immunity from original vaccinations.Most people in the United States have failed to get a COVID-19 booster vaccine because of pervasive booster vaccine hesitancy, compromising public herd immunity.

COVID-19 continues to be a significant public health issue, related to both morbidity and mortality because of waning immunity from original vaccinations.

Most people in the United States have failed to get a COVID-19 booster vaccine because of pervasive booster vaccine hesitancy, compromising public herd immunity.

Public health significance—Why is this work of significance to public health?
Use of diffusion of innovation theory and qualitative methods provides key insights into how different adopter groups conceptualize barriers to COVID-19 booster vaccine uptake.Findings can be used to develop public health interventions that address specific concerns, especially in those least likely to get a COVID-19 vaccine booster.

Use of diffusion of innovation theory and qualitative methods provides key insights into how different adopter groups conceptualize barriers to COVID-19 booster vaccine uptake.

Findings can be used to develop public health interventions that address specific concerns, especially in those least likely to get a COVID-19 vaccine booster.

Public health implications—What are the key implications or messages for practitioners, policy makers and/or researchers in public health?
Given diffusion of innovation theory’s application to other health behaviors, it provides a viable framework to analyze willingness to receive COVID-19 booster vaccinations.Messaging about COVID-19 booster vaccinations may have to be tailored to unique concerns by diffusion of innovation adopter groups.

Given diffusion of innovation theory’s application to other health behaviors, it provides a viable framework to analyze willingness to receive COVID-19 booster vaccinations.

Messaging about COVID-19 booster vaccinations may have to be tailored to unique concerns by diffusion of innovation adopter groups.

COVID-19 vaccine hesitancy is well documented, but less is known about booster hesitancy among fully vaccinated adults. A qualitative approach was employed to identify factors affecting COVID-19 booster hesitancy using diffusion of innovation (DoI) theory. The study was conducted in Philadelphia, Pennsylvania. In-depth interviews (n = 30) were done with adults, including those who had (n = 9) and had not (n = 21) been boosted. Participants were categorized into DoI adopter groups or a “refuser” group for those with no intention of getting boosted. Transcripts were analyzed using an iterative coding process with consensus and triangulation to develop thematic categories. Participants had a mean age of 41 and were 63.3% Black; 20% were classified as innovators, 6.7% early adopters, 3.3% early majority, 6.7% late majority, 43.3% laggards and 20% refusers. Three themes varied across groups: level of perceived risk susceptibility of getting COVID-19 in the future, information needs and levels of vaccine literacy, and effects of ongoing institutional mistrust. Those in the laggard and refuser groups generally had lower vaccine literacy, higher levels of institutional mistrust, and were more likely to listen to friends and family for booster advice, all consistent with DoI adopter characteristics. These differences indicate important intervention targets to promote booster uptake, especially in those who have been previously vaccinated.