Wording of vaccination messages influences behavior

Young adult subjects in the study recently published in the journal Health Communication were more interested in learning about the HPV vaccine when exposed to messages that were both injunctive and normative -- meaning statements that implied their friends and family thought they should get the vaccine -- versus messages that gave basic information about the vaccine's benefits.

The subjects were also less likely to be interested in the vaccine when they received descriptive messages that were negatively worded: for instance, ones that said that 3 out of 10 people missed out on the HPV vaccine.

"We should be careful about using these types of messages," said Porismita Borah, an associate professor in WSU's Edward R. Murrow College of Communication and one of the study's authors. "Whether you say that 3 out of 10 did not get the vaccine, or that 7 out of 10 did get it -- that makes a difference. It influences people's attitudes and behavior."

Many health organizations, including the World Health Organization and the CDC, often use these types of negatively worded, norm-based messages, but this is the first experimental study that tested the influence of social norms on behavior.

More than a decade of research has supported the HPV vaccine's safety and effectiveness in preventing genital warts and cancers associated with the sexually transmitted infection including cervical, anal and penile cancer. Yet according to the CDC, the vaccine has a low uptake in the United States with 48.5% of women and 78.8% of men aged 19 to 26 remaining unvaccinated, pointing to the need for better promotional messaging.

For the study, Borah and Xizhu Xiao, a recent WSU Ph.D. graduate, tested messages on nearly 200 young adults between the ages of 18 and 29. The participants were randomly assigned into four groups that each received a different set of messages about the HPV vaccine based on social media posts typically used by health organizations. They found that the negatively worded normative messaging frequently increased vaccine risk perceptions, compared to the positively worded normative and basic information messages.

Also, the students who were exposed to the injunctive normative messages had a greater intention to seek vaccine information, which in turn increased their intention to get the HPV vaccine.

"This study implies that using messages that highlight the importance of others' approval of vaccination, such as parents and peers, may be especially helpful in piquing individuals' interest to get more information about the vaccination. The information seeking in turn is likely to raise their intention to get vaccinated," said Xiao.

While the authors cautioned that this study was limited and specifically focused on promotional messages for the HPV vaccine, they did say the results may have some implications for the promotion of other vaccinations, including a potential COVID-19 vaccine.