Efficacy information influences intention to take COVID-19 vaccine

A successful response to the COVID-19 pandemic requires achieving high levels of vaccine uptake. We tested whether directly contrasting the high efficacy of COVID-19 vaccines with the lower efficacy of the annual flu vaccine would increase intentions to take a COVID-19 vaccine.

A pre-registered online study of 481 participants compared four information conditions: (1) no information; (2) COVID-19 Vaccine Information Only; and COVID-19 Vaccine Information combined with flu vaccine information suggesting either (3) 60% efficacy or (4) 40% efficacy; we measured COVID-19 and flu vaccine intentions along with several other vaccine-related variables.

The Prolific platform was used to recruit 481 UK participants (64% female; aged between 18 and 85 years) who had been pre-screened to have intermediate levels of vaccine hesitancy. After reading a short text (~200 words) about COVID-19 vaccines, participants were asked about their vaccination intentions.

Providing information about the safety and efficacy of the new COVID-19 vaccines resulted in vaccination intentions that were, on average, 0.39 standard deviations (SDs) higher than those in the no information condition; providing the same COVID vaccine efficacy information in the context of information about flu vaccine efficacy resulted in a further significant increase in vaccination intentions that were 0.68 SD higher than those in the no information condition. This positive contrast effect for the COVID-19 vaccine was not associated with reduced flu vaccine intentions.

Vaccination intentions can be strengthened through a simple messaging intervention that utilizes context effects to increase perceived response efficacy.