A Path Analysis Model Suggesting the Association between Health Locus of Control and Compliance with Childhood Vaccinations

"The strength of this study is in adding the variable health locus of control as part of the determinants that can influence parents in their decision to vaccinate their child."

Health locus of control (HLOC) refers to an individual's perceptions of the importance of factors governing his or her own health or illness. Internal LOC refers to the extent to which individuals believe in their own ability to influence their health status; in contrast, others may believe that their health depends upon external factors such as God, chance, or other people. Considering that internal or external HLOC may be a factor influencing vaccine hesitancy, this study investigated the relationship between parents' HLOC and compliance with routine childhood immunisation programmes in Israel.

In Israel, the National Immunization Program (INIP) includes vaccines against 13 diseases. The INIP is non-mandatory and free of charge for every child residing in Israel. The vaccines are administered in Mother-Child Health Clinics (MCHCs) located all over the country. Overall, vaccine coverage is 90%, but, occasionally, Israel experiences outbreaks of vaccine-preventable diseases such as measles in small communities with low vaccine coverage.

This was a stratified case-control study with a retrospective cohort. Two groups of parents of children aged 3-4 years from north and central Israel were interviewed by telephone between December 2012 and March 2013: 309 parents of children who had not completed one or more of the vaccinations recommended (the study group) and 422 parents of children who had completed the recommended vaccinations (the control group).

Internal HLOC, chance HLOC, and powerful others HLOC (the latter two representing external HLOC) were measured; for example, question for internal HLOC: "When my child is ill, I have the power to make him well again"; question for chance HLOC: "I often feel that no matter how many vaccines my child might get, if she is going be ill, she will be"; and for powerful others HLOC: "If my child regularly visits the MCHC, he is less likely to have health problems". Beliefs in reliability of information sources regarding vaccines were divided into two groups: (i) formal sources of information; for example: "To what extent do you perceive the MCHC nurses as reliable?" and (ii) informal sources of information; for example: "To what extent do you perceive the internet sites that oppose vaccination as reliable?". Finally, three groups of attitudes were measured: (i) pro-vaccine attitudes (Pro VA); (ii) anti-vaccine attitudes (Anti VA); and (iii) attitudes regarding mandatory vaccination (Mandatory VA). Path analysis was conducted to explore direct and indirect associations between HLOC and vaccination compliance.

Among the study's findings were that:

• Internal HLOC and powerful others HLOC among parents in the study group were significantly lower than those in the control group.
• Chance HLOC was significantly higher among parents of the study group than those in the control group.
• High powerful others HLOC was found to have a direct association with vaccination compliance.
• High internal and chance HLOC have indirect associations through parents' attitudes regarding vaccines.
• Perceived reliability of information sources was associated with not complying with vaccines.

Thus, in the current study, internal LOC, chance HLOC, and powerful others HLOC explain full compliance with childhood vaccination directly and through mediating factors. Powerful others HLOC predicts direct compliance with childhood vaccinations, but an indirect path can explain this phenomenon as well. For example, internal HLOC might follow this path: As internal HLOC increases, positive attitudes regarding vaccinations increase, leading to a higher probability of full vaccination. On the other hand, for those not compliant with childhood vaccination, chance HLOC might follow this path: As chance HLOC increases, positive attitudes regarding vaccinations decrease, and negative attitudes regarding vaccinations, attitudes against mandatory vaccinations, and reliability of informal sources that opposed vaccinations increase, leading to lower levels of children's vaccinations.

Implications of the findings are outlined. "From a public health perspective, there may be a paradox: On the one hand, we are interested in parents who vaccinated their children with full understanding of the importance of vaccinations, in their safety and necessity. On the other hand, we are not interested in parents who have 'blind faith' in nurses or doctors who care for them. We aspire to the public with the ability to make a sophisticated medical decision, based on professional and reliable information. Therefore, it is important to deepen the parents' knowledge of vaccines in order to prevent passivity or ignorance regarding the vaccinations of their child."

Proposed actions to strengthen the public's confidence in the professional health care include actions at the micro and macro levels:

• Micro-level activities include enriching knowledge among medical staff and providing practical tools, based on a positive attitude and effective communication with the parent, to cope properly with parents' hesitation in vaccinations or parents who refuse one or all vaccines. The medical staff should be able to tailor a specific intervention programme to vaccine-hesitant parents according to their needs.
• At the macro level, policymakers should use sophisticated social media to engage with people seeking information online (informal sources of vaccination information) in order to encourage public trust in medical staff. Programmes for the general public that engage in critical reading of informal medical information on websites may also increase the public's trust in the medical establishment. As this study suggested, such programmes may act as a balance between chance HLOC and powerful others HLOC and may encourage hesitant parents to vaccinate their children.