Effect of risk communication format on COVID-19 vaccine-related risks

By Tarun Sai LomteFeb 2 2023Reviewed by Aimee Molineux

In a recent study published in Healthcare, researchers investigated the association between risk-communication format and perceived coronavirus disease 2019 (COVID-19) vaccine-related risks.

Vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a crucial strategy to prevent severe COVID-19. However, fear of vaccine-related adverse events and side effects may impact vaccine uptake. Recently, studies have demonstrated that adults highly fear vaccine-related side effects. These risks are currently described using verbal terms; although well-intended, this might be problematic since the format of risk communication can influence risk perceptions and decision-making.

 About the study

The present study evaluated how risk communication format affects COVID-19 vaccine-related risk perceptions. They conducted an online survey in January 2022 in the United States (US) among adult individuals recruited using a crowdsourcing platform, Mechanical Turk (MTurk). Eligible subjects were aged 18 – 90 with an MTurk rating above 98%.

Individuals who did not receive all primary and booster vaccinations were randomized to receive information on three side effects (fatigue, fever, and headache) and one adverse event (myocarditis) after COVID-19 vaccination using numerical risk estimates or verbal descriptors. Myocarditis was described as a rare event (verbal) or 0.001205% (numerical), while fever, fatigue, and headache were described as common or 8%, 47%, and 41%, respectively.

Participants rated their perceived risks of developing side effects after their indicated vaccine dose on a scale of 100%. The survey was designed to also capture information on demographics and political identity. Participants’ intention to take the next vaccine dose was assessed, and they were stratified as vaccine-accepting, -rejecting, -deferring, or hesitant based on responses.

Participants reported the impact of distinct information sources on COVID-19 vaccines, such as social media, healthcare professionals, loved ones, news media, religious, school, or work community, and public health organizations. A linear regression model examined the impact of verbal and numerical descriptors on perceived risk(s).

Findings

In total, 939 individuals participated in the online survey. Of these, 575, 61, and 303 were fully, partially, and not vaccinated, respectively. Participants’ average age was 39, and 55.6% were males. There were 444 participants randomized to verbal descriptors and 495 to numerical descriptors. Participant characteristics were balanced between groups.

The mean risk perceptions were more variable and higher in the verbal descriptor arm for the common side effects. The largest difference (between groups) was for fever, with an estimated risk of 41.4% in the verbal descriptor arm against 15.4% in the numerical descriptor arm. Differences between groups were smaller for fatigue and headache.

Standard deviations were much larger for each side effect in the verbal descriptor arm, suggesting more variability in risk perception with verbal risk descriptors. Multivariable analysis revealed that verbal descriptors were linked to a higher perceived risk for vaccine-related side effects. Increased social media influence or political identity was not associated with differences in perceived risks.

Vaccine-rejecting and -deferring individuals had a higher perceived risk of fatigue and headache than vaccine-acceptors. Vaccine-hesitant individuals showed no increase in risk perceptions. Participants exposed to the verbal descriptor (rare) had a higher perceived risk of myocarditis than those in the numerical descriptor arm. Multivariable analysis showed an association between verbal descriptors and a higher perceived risk of myocarditis.

Individuals influenced by social media also had an increased risk perception for myocarditis. A lower perceived myocarditis risk was observed for individuals with a more liberal political identity. Vaccine-hesitant and -deferring individuals had lower perceived myocarditis risks than vaccine-accepting respondents. Male sex was associated with a lower perceived risk of side effects and myocarditis.

Conclusions

The online survey results indicated that verbal descriptors resulted in more variable, less accurate, and elevated perceived risk of COVID-19 vaccine-related side effects than numerical descriptors. The findings highlight the potential value of transitioning from verbal descriptors to numerical risk estimates. Respondents in the verbal descriptor arm consistently reported risks between 40% and 50% for vaccine-related side effects.

However, there were minor differences between estimated risk perceptions and published risk estimates. The median perceived myocarditis risk was more than 1000 times greater for verbal descriptors than numerical estimates. Taken together, verbal descriptors of COVID-19 vaccine-related risks may increase risk perceptions among adults. Individuals highly influenced by social media may have heightened risk perceptions regardless of the communication format.