A Systematic Review of Factors Affecting Vaccine Uptake in Young Children

"If uptake of routine child vaccination is to increase, public health communications about vaccines must be informed by evidence on the factors affecting uptake."

This systematic review investigated psychological, social, and contextual factors associated with uptake of routine vaccines among healthy children aged 5 and under in high-income countries (where, unlike in developing countries, some parents make conscious decisions not to use readily available vaccines). Studies were included if they reported analyses of the association between psychological factors and uptake or included parents' self-reported reasons for or against vaccination. Sixty-eight citations describing 64 studies were included.

Predictors and reasons for or against vaccinating are summarised in Tables 1 and 2 in the paper. In brief, there is strong evidence for an association between vaccination uptake and: not perceiving vaccines to cause adverse effects; general positive attitudes towards vaccination; positive vaccine recommendations; and perceiving fewer practical difficulties of vaccination. While there was good evidence for an association between vaccination and perceived susceptibility to the illness, evidence for an association between perceived severity of an illness and vaccination was weak. Other factors associated with vaccination include knowledge about the vaccine, social influences (e.g., other parents don't vaccine child either), and trust in the healthcare profession. Having increased information about the vaccine was associated with vaccination, but more research is needed on the influence of information to improve the content and dissemination of public health messages. Messages could focus on increasing individuals' capability, opportunity, and motivation to vaccinate their child, as suggested by the behaviour change wheel.

Reflecting on the findings, the researchers point out that, in line with findings from previous reviews of child vaccination and wider reviews of medication adherence, perceiving vaccination to cause adverse effects was consistently associated with vaccine refusal. While there was strong evidence of an association between low perceived susceptibility to an illness and vaccine refusal, evidence for a role of perceived illness severity was weak. Thus, the researchers recommend that future communications focus on children's susceptibility to an illness rather than severity of the illness.

The researchers found no experimental studies using interventions to alter parental attitudes using vaccination uptake as an outcome (vs. outcomes only measured as a change in attitudes or intentions) for this age group. They suggest that this is a logical next step for vaccine uptake research. Other intervention studies have investigated the impact of additional reminders through new modes of communication, such as text message reminders, rather than investigating the content of different messages. This review highlights factors that could be targeted by such messages. In addition to addressing concerns over vaccines causing adverse effects and focusing on children's susceptibility to the illness, suggestions include promoting the belief that the vaccine is effective, increasing parents' knowledge of the vaccine schedule, and ensuring that all healthcare providers recommend vaccination.