Do Norms Matter? Examining Norm-Based Messages in HPV Vaccination Promotion

"Conducting injunctive norm-based campaigns may help increase people's intention to obtain more knowledge about the vaccine and subsequently promote higher intention to get vaccinated."

Despite efforts to identify promotional strategies to increase human papillomavirus (HPV) vaccination-related outcomes, vaccine uptake remains insufficient in the United States (US), where data show that 48.5% of females and 78.8% of males aged between 19 and 26 remain unvaccinated or under-vaccinated. Media - social media in particular - are one factor contributing to misinformation surrounding the vaccine and the formation of anti-vaccination sentiment. Grounded in literature on norms, this study involved a 4-condition, between-subject experiment to examine: (i) the effectiveness of norm-based messages in influencing HPV vaccination-related intentions and risk perceptions; (ii) whether negatively worded normative messages demonstrate equivalent effectiveness as positively worded ones in HPV vaccination promotion.

The concept of perceived norms includes:

• Descriptive norms, which refer to people's perceptions about what most people are doing. They provide a decision-making shortcut, which is based on a presumption that if everyone is adopting a behaviour, one would think that the behaviour must have some merits and that it is sensible to also adopt the behaviour. Although prior research and practices have often operationalised descriptive norms using positively worded messages, there are examples of negatively worded messages as well (e.g., in a 2019 Instagram post, the World Health Organization (WHO) wrote: "More than 1 in 10 children missed out on lifesaving vaccines").
• Injunctive norms, which refer to what is approved or disapproved of by others. They motivate behaviours by promising social rewards and punishments (informal sanctions). Multiple studies have demonstrated the validity of injunctive norms in predicting vaccination-related intention, and the use of injunctive normative messages is recommended when performing an unhealthy behaviour (e.g., not vaccinating against HPV) is a societal norm.

A total of 190 US college students ranging in age from 18 to 29 participated in the study. Participants in the normative message conditions were exposed to 2 Facebook posts (a basic information post and a norm-based Facebook post), whereas those in the basic information condition were only exposed to the basic information post. Following the conceptualisation of perceived norms, message stimuli were associated with a credible source: the US Centers for Disease Control and Prevention (CDC).

The basic information post contained factual information about HPV and HPV vaccination. The positively worded descriptive normative post was phrased: "7 out of 10 college students received the lifesaving HPV vaccine for cancer prevention." The negatively worded descriptive normative post was phrased: "3 out of 10 college students missed out on the lifesaving HPV vaccine for cancer prevention." The injunctive normative post highlighted the approval of receiving the HPV vaccines: "Your peers and loved ones think you should get the HPV vaccine for cancer prevention."

Results showed that participants were more interested in learning about the HPV vaccine when exposed to messages that were both injunctive and normative - statements that implied their friends and family thought they should get the vaccine - versus messages that gave basic information about the vaccine's benefits. This increased intention to seek further information about HPV vaccination in turn enhanced intention to get the vaccine. Negatively worded descriptive normative messaging resulted in the highest risk perceptions of the HPV vaccine, compared to positively worded descriptive norms and basic information messages.

Among the practical implications are:

• Using messages that highlight the importance of others' approval of vaccination, such as parents and peers, may be especially helpful in piquing individuals' interest; and
• Via the phenomenon of reactance, which is often evoked by messages highlighting the negative costs of not enacting desired behaviours, focusing on the costs of not getting the vaccine may debilitate the credibility of the messaging and raise suspicions about the vaccine. Therefore, health practitioners are advised to use positively worded descriptive norms or simply disseminate basic information regarding the vaccine in practice.