This evidence review was compiled by members of the CITF Secretariat with the input from experts affiliated with the CITF and does not necessarily reflect the views of all CITF members.

In this Canadian study published in JAMA, researchers wanted to know if the type of information provided about a vaccine could affect people’s likelihood of accepting it. Findings indicate that providing information on how well vaccines prevent death, rather than how well they prevent symptomatic disease, made participants more likely to accept the vaccine.

The research team carried out an online survey with a group of Canadians representative of the general population. Respondents were randomly assigned a vaccine (Oxford-AstraZeneca or Janssen-Johnson & Johnson) and were provided information about their assigned vaccine’s effectiveness against death or its overall effectiveness at preventing symptomatic COVID-19. An additional group of participants received both pieces of information about their assigned vaccine, whereas a control group only received the following information “Health Canada has recently approved the [AstraZeneca/Johnson & Johnson] vaccine.” Finally, all respondents were asked “How likely would you be to take this vaccine if offered to you?” Their answers could be “very likely, somewhat likely, not very likely, or not at all likely”. A total of 2556 participants completed the questionnaire, of which 52% where women, with a median age of 50 years (34-63 years-old).

Key findings:

  • Intention to receive the vaccine and perceived vaccine effectiveness were higher among respondents who were told about the vaccine’s ability to prevent death, compared to those who were not given this information
  • Intention and perceived vaccine effectiveness were lower among those given information on the overall efficacy of their assigned vaccine compared to those who were not.
  • Providing information on death prevention did not have an impact on the negative association between overall efficacy information and the likelihood of accepting a vaccine.
  • Women who received information on death prevention were more likely to intend to get vaccinated, compared to women who were not given that information. This was also observed among respondents within the age group of 35 to 54 years when compared to other age groups.
  • Receiving both pieces of information did not increase intention to receive the vaccine.

This study provides evidence that communications around vaccine effectiveness should focus on how well they prevent death rather than the perceived less impressive metric of how well they prevent symptomatic disease.

Merkley E, Loewen PJ. Assessment of Communication Strategies for Mitigating COVID-19 Vaccine-Specific Hesitancy in Canada. JAMA Netw Open. 2021 Sep 1;4(9):e2126635. doi: 10.1001/jamanetworkopen.2021.26635