Determinants of Human Papillomavirus Vaccine Acceptance among Caregivers in Nigeria: A Fogg Behavior Model-Based Approach

"The urgency of meaningful communication, social mobilization, and community engagement in enhancing the vaccine's acceptability among caregivers cannot be overstated....This requires first understanding and then addressing caregiver concerns regarding the HPV vaccine."

Human papillomavirus (HPV) vaccine uptake among adolescent girls is critical to reducing the burden of HPV-related cancers in Nigeria. However, low levels of involvement among the caregivers of adolescent girls in vaccination efforts and limited knowledge of the vaccine among caregivers have been identified as potential barriers to vaccine adoption. This study assesses the factors influencing caregivers' acceptance of HPV vaccination for their charges, using the Fogg Behavior Model (FBM) as a theoretical framework. The FBM posits that behaviour happens when three factors co-occur: motivation, ability, and prompt. This study captured data on motivation and ability because of their significant impact on vaccine uptake behaviours in Nigeria.

The HPV vaccine was introduced in Nigeria on October 24 2023 with Gavi support, which commenced on 24 October 2023. Survey data collection was conducted in August and September 2023 and provides a true baseline against which the programme progress may be measured. A follow-up survey is planned for March 2024 to determine the level of vaccine uptake following its introduction.

Using a survey instrument based on the FBM, the researchers analysed cross-sectional data from 1,429 caregivers of girls aged 9-17 in six Nigerian states. Participants were recruited via Facebook and Instagram advertisements and interviewed through Facebook Messenger. The researchers applied bivariate and multivariate analyses to assess the relationships between the caregiver's perception of how likely their adolescent girl was to get vaccinated in the next 12 months (the primary outcome measured) and motivation, ability, social factors (such as discussions with family and friends), injunctive norms, previous COVID-19 vaccination, and respondents' sociodemographic characteristics.

Select findings include:

• Most caregivers (60%) believed that it was very likely that the female child in their care would get vaccinated in the next 12 months.
• Caregivers' motivation to have their female child vaccinated was high: 73% of caregivers considered it very important to have their adolescent girl vaccinated against HPV.
• Caregivers' level of ability to have their adolescent vaccinated was low: only 20% of caregivers strongly disagreed with the statement that it was difficult to have their female child vaccinated against HPV.
• Knowledge of the HPV vaccine was very low, with only 18% of caregivers able to correctly respond to 4 questions asked to gauge their level of knowledge of HPV vaccination.
• Most caregivers (72%) were very likely to discuss HPV vaccination with their family and friends.
• About one-third of respondents believed that most of their family and friends approved of girls getting the HPV vaccination, an injunctive norm.
• 32% of respondents reported they had not received a COVID-19 vaccination, a variable that the researchers interpret as a proxy for COVID-19 vaccine hesitancy.

Adjusted odds ratios derived from logistic regression analyses revealed that:

• Motivation was associated with a caregiver's perception that their female child would get vaccinated in the next 12 months: 70% of caregivers who had high motivation believed this compared to 33% of other caregivers. In other words, caregivers with high motivation had a 2.30 times higher odds ratio of believing that their adolescent girls would receive the HPV vaccine, compared to other caregivers.
• High ability was also associated with a higher proportion of caregivers believing that their female child would get vaccinated in the next 12 months (76%) compared with other caregivers (56%). In other words, caregivers with high ability were 1.69 times more likely than other caregivers to believe that their female child was very likely to get vaccinated.
• There was a significant positive relationship between knowledge of the HPV vaccine and the outcome: 75% of caregivers who had the maximum score of 4 on the knowledge index believed that their adolescent girl would get vaccinated compared with 50% of caregivers who had a score of 0-1.
• Caregivers who perceived that their family and friends were supportive of the HPV vaccination were more likely to believe that their female child would get vaccinated (79% versus 52%). In other words, the injunctive norm was associated with a 1.74 times higher odds ratio of a caregiver believing that HPV vaccination was very likely.
• A caregiver who was very likely to discuss HPV vaccination with family or friends had a 4.78 times higher odds ratio of believing that their adolescent girl would get vaccinated against HPV.
• Consistent with the idea that COVID-19 vaccine hesitancy may influence HPV vaccine uptake, caregivers who had not received a COVID-19 vaccination were less likely to believe that their adolescent girl was very likely to get vaccinated in the next 12 months (49% vs. 66%), which is the equivalent to an adjusted odds ratio of 0.71.
• Caregivers in cities were more likely to believe that their female child would get vaccinated in the next 12 months, with a 1.26 times higher odds ratio.

Future research could explore the underlying reasons for the observed associations and how best to design interventions that address the identified barriers and facilitators of HPV vaccine uptake.

In reflecting on the findings, the researchers note that the association between motivation and the perceived likelihood of vaccination is consistent with the FBM. They recommend interventions targeting multiple factors to increase HPV vaccine uptake, including:

• Interventions that leverage positive family and peer influences and increase discussion of HPV vaccination among members of caregivers' social networks;
• Efforts to simplify the vaccine adoption process, reduce costs, and increase vaccine access, particularly since the level of ability of Nigerian caregivers is very low (20%).
• Improving knowledge about HPV vaccination through educational campaigns; and
• Addressing vaccine hesitancy more broadly, which may have a beneficial impact on the acceptance of both HPV and COVID-19 vaccines.

In conclusion, this study "highlight[s] the importance of motivation, ability, and social factors in driving the acceptability of HPV vaccination in Nigeria. It suggests that multi-faceted interventions that influence the ability of caregivers and the social influence upon them are important in addition to efforts to reduce vaccine hesitancy more broadly. Interventions should be designed at multiple levels, with the focus being on helping individuals overcome the range of barriers that they face - many of which exist at a level beyond their individual control."