Health Literacy and Vaccination: A Systematic Review

This systematic review aims to describe the state of the art in the relationship between health literacy (HL) and the attitude towards vaccines, intention to vaccinate, and vaccine uptake. The goal is to examine the role of health literacy or illiteracy as a determinant of vaccination hesitancy.

As described here, the concept of 'vaccine literacy' looks at HL from the point of view of vaccine attitudes and hesitancy in order to better define and understand the main determinants of vaccine uptake. Ratzan (2011) describes vaccine literacy as "not simply knowledge about vaccines, but also developing a system with decreased complexity to communicate and offer vaccines as sine qua non of a functioning health system." The authors of the review point out that comprehending vaccine information requires certain literacy and numeracy skills, which is why communicating the information to patients is a challenge, particularly if the patients have low HL. Moreover, critical and evaluation skills are required to seek out the right information, especially considering the ever-increasing amount of information in the media, particularly on the internet. "In such a scenario, HL, and specifically vaccine literacy, can influence vaccine uptake."

The following databases were explored from January 1 2007 to January 15 2017: PubMed, Embase, PsycINFO, ERIC, Health Evidence, Centre for Reviews and Dissemination, Scopus, Web of Science, and Cochrane Library. Included were primary studies that investigate the link between HL and behaviour towards vaccination - whether vaccination awareness and knowledge, compliance with recommended child vaccinations, or immunisation status. The research investigated all kinds of vaccines, without geographic limits.

So far, the relationship between HL and vaccination has been investigated only to a limited extent. All the 9 studies included in the final synthesis were observational ones. They were primarily based on cross-sectional designs, though one was a longitudinal-prospective cohort study. The approach for measuring HL varied among different studies. In one case, an HL tool evaluated communicative (development of personal skills) and critical (personal and community empowerment) HL in addition to functional HL, which refers to the capability to transmit real information on vaccinations. In doing so, it provided a more comprehensive measure of HL. The studies mainly investigated whether HL influences attitudes towards vaccinations.

Different outcomes were noted. Considering the association between HL and the attitudes of parents towards vaccinations, one study revealed that communicative HL had a significant negative direct association with vaccination compliance. The study found functional HL and critical HL to have an indirect effect, mediated through other variables, on completion of the vaccination protocol. This suggests that parents with highly functional, communicative, and critical HL are more at risk of not vaccinating their children. In contrast, a study conducted in India suggested that maternal HL was independently associated with child vaccination. This study revealed a positive association between maternal HL and the diphtheria-tetanus-pertussis vaccination for children.

"The relationship between HL and vaccinations seems to be driven by risk perceptions and by the likelihood of getting sick or suffering from complications in the short term. When these possibilities are high, HL positively predicts vaccination uptake; when they are low, HL negatively predicts vaccination uptake or shows no effect. This aspect is particularly relevant in the context of parents. For them, the balance between the perceived benefits and the perceived barriers is driven by a sense of responsibility towards their child. This highlights the multifaceted nature of their choices regarding vaccinations."

In short, the role of HL in predicting vaccine hesitancy or acceptance seems to be influenced by a few key factors. These include country, age, and type of vaccine. However, the relationship between HL and vaccination remains unclear. New research studies are needed - particularly longitudinal ones that use multiple measurement tools. Tools that are specific to vaccine literacy and those used to measure general HL would ensure a more comprehensive assessment of HL, thus leading to a better understanding of the role played by HL in predicting vaccine uptake or moderating the effect of other determinants of vaccination behaviours.

The researchers suggest that, "To create conditions of better health for all, and consequently promote health interventions like vaccinations, people should receive support for their decisions. Community action should be reinforced to create empowerment and health services should be reoriented to bring them closer to citizens. Vaccine hesitancy is a defeat of people's empowerment; hence, it must be fought in every possible way and the improvement of HL is essential for it. Specific information and training interventions are needed at various levels. These should aim at increasing awareness on vaccine-preventable infectious diseases and vaccinations."