Factors Influencing Childhood Influenza Vaccination: A Systematic Review

"The findings can inform further studies on factors influencing childhood influenza vaccination in lower/middle-income countries...and finally contribute to country-level policy decisions and improve childhood influenza vaccination uptake."



Childhood influenza vaccination coverage remains low in lower/middle-income countries. Numerous factors contribute to the low influenza vaccination coverage in countries and regions. The World Health Organization (WHO)'s Strategic Advisory Group of Immunization (SAGE) proposed in the Vaccine Hesitancy Determinants Matrix that individual/social influences, contextual influences, and vaccine and vaccination-specific issues all play a role. This systematic review summarises the literature on factors influencing childhood influenza vaccination among a variety of populations from a diverse set of geographical and cultural contexts.



A systematic review of literature published before December 2019 was conducted and included empirical studies with original data that investigated factors influencing childhood influenza vaccination. A standardised form based on Cochrane Review and behavioural theories including the Knowledge, Attitude, and Practices model, the Health Belief Model, and the Theory of Planned Behavior was developed specifically for this review prior to data extraction. Topics in the form include knowledge and awareness of influenza and influenza vaccines, perceived susceptibility and severity of influenza, benefits and barriers to influenza vaccination, cue to action and social norms, self-efficacy, emotions, and confidence in the importance, safety, and efficacy of influenza vaccines.



Thirty studies from eight countries were included in the analysis. The majority of included studies adopted quantitative methods. The studies detail a wide range of childhood influenza vaccination coverage (4.04-96.4%) and caregivers' intention (48-85.1%) to vaccinate their children. In general, childhood influenza vaccine coverage rates in high-income countries and regions are higher, which may be due to a better vaccination infrastructure and free flu vaccinations; however, it is worth noting that vaccination rates in high-income countries and regions are still far from ideal.



The included studies found that childhood influenza vaccination was positively associated with caregivers' knowledge of influenza vaccine, positive vaccine attitudes, self-efficacy, perceived susceptibility and severity of influenza, believing in the efficacy of influenza vaccine, the worry of getting sick, and previous influenza vaccination experiences. Also, among the included studies, research frequently explored communication about vaccines between caregivers and healthcare workers (HCWs), family members, and other potential information sources, as well as caregivers' perception of others' vaccination behaviour (regarding behaviour exhibited by others as sensible), and self-rated health status of themselves or children. Studies in Singapore, United States, England, and Thailand all indicated that having had a healthcare worker recommend vaccination (odds ratio (OR) = 2.8-8.2, percentile rank (PR) = 1.47-2.47) could increase childhood influenza vaccination. Increased intention to get children vaccinated was also observed among caregivers whose healthcare professionals had recommended vaccination (OR = 1.11) or social influence of family or others.

 

Concerns about vaccine safety and side effects seem to have been the main barriers determining caregivers' willingness to vaccinate. Poor access to vaccination service was another challenge.



Based on the review, the researchers suggest that:

• Health education, and providing adequate, clear, and accessible information to caregivers about influenza infection and vaccines, could increase caregivers' understanding of vaccines.
• Communication efforts, such as health communication techniques on a variety of media platforms, are needed to leverage the positive themes that emerged from the study as encouraging high vaccine uptake, including the rigorous safety process in vaccine development and approval by the drug administration authority entities.
• Studies on contextual factors, including the procurement and supply of vaccines and the promotion of vaccines by the health sector, are needed to provide insights into how contextual factors can drive public vaccination behaviours.
• Factors at different levels, including knowledge and confidence in vaccines, workload, communication skills, financial incentives for recommending vaccines, and whether vaccines are free or not, all influence the recommendation behaviour of HCWs. Further research into these and other factors is needed to optimise the communication between HCWs and the public.
• Continued research is needed to understand how public perceptions of influenza changed during COVID-19 and to develop more effective and comprehensive strategies to promote vaccination.
• The use of standardised tools for collecting information about respondents' knowledge on influenza viruses and vaccines, similar to ones available for other vaccines, could facilitate more consistent data collection and enable researchers to more accurately compare the knowledge level and perceptions among people in different countries and regions.
• More qualitative studies are needed to provide insights into the formation of caregivers' attitudes and perceptions, allowing deeper understanding beyond predetermined quantitative tools.