The National Health Performance Authority’s report on childhood vaccination coverage released this morning shows immunisation rates have slightly increased in 2011-2012. But there are still some areas where coverage is below the national target.

The good news is that Australia has one of the highest vaccination rates in the world with over 90% of children fully immunised by age five. But there are areas where only 80% of five-year-olds are protected against preventable contagious disease.

So why are some children not immunised? There are two broad influences on timely uptake of routine childhood vaccines – access and acceptance.

Understanding access and acceptance

Access is partly a structural problem, linked to barriers such as a lack of transport, limited clinic opening times, home-boundedness and, beyond that, to poverty and social exclusion. Generally speaking, we can address access problems by minimising these barriers.

But because access issues stem from social determinants of health such as location, education level, income and opportunity, they’re necessarily “sticky” problems. They can’t be changed quickly or easily but once they are, the change can be maintained.

Research and experience indicate that about half of under-immunisation in Australia is due to lack of access.

The other factor impacting vaccine uptake is acceptance. This is the psychological orientation to vaccines influencing uptake; it’s about attitudes, beliefs and concerns regarding vaccines, parenting, medicine generally, and a host of related matters. An individual’s vaccine acceptance is the result of a certain composition of these, like a metaphorical DNA.

Vaccine acceptance can be dynamic, shifting in response to new information. Unlike vaccine uptake, which is an either-or behaviour, it covers a continuum from total acceptance to complete vaccine rejection.

Interestingly, acceptance can erode with no visible change in behaviour until a tipping point at which a parent will begin to delay or refuse some or all vaccines.

Hesitancy and refusal

The public tends to hear a lot more about acceptance factors than they do about access. It’s an easy formula for mass media to pit vaccination opponents against proponents, and parade examples of non-vaccinating parents. It excites emotion, leading to high click rates in online articles and crowded comments pages.

Nevertheless, the attention given to such parents is out of proportion to their actual numbers, and the likelihood of changing their minds. Vaccine refusers are a very small proportion in Australia – about 2% of parents make a values-based choice to forego all vaccines for their children.

A more interesting group is the 12% of parents who are at least somewhat supportive of vaccination, but fear both vaccination and non-vaccination could have negative outcomes for their child. About half of that 12% vaccinate fully, and the other half may delay or avoid certain vaccines but will have others.

This “hesitant” group should be differentiated from vaccine refusers, and efforts to increase vaccine acceptance should focus on these parents. Remember that these people already have the motivation to vaccinate, and they’re a much larger group than non-vaccinators.

Understand first

Any action taken at the community level starts with acknowledging that parents want the best for their children regardless of their access to and acceptance of vaccines. When otherwise well-intentioned messages criticise what these parents view as healthy skepticism, the result can be a further distancing from timely uptake.

There are three broad strategies for increasing vaccination rates. Improve access to vaccines for those who need it, address the concerns of hesitant parents, and help non-vaccinators see immunisation as a safe and effective way of protecting their children’s health.

But these broad strategies need to be fleshed out with detail. For that, we need to address other questions, such as how to determine whether low coverage is due to low access, hesitancy, or refusal. Also, what specific concerns and values give rise to hesitancy and refusal, and which of these values are most amenable to change.

A strong understanding of the causes of under-immunisation will help us formulate effective responses to it. A strong understanding will also improve the quality of the national conversation about vaccination, helping us move beyond assumptions and reactions to a more thoughtful engagement with issues and barriers.

Ultimately, a better understanding of why people accept or refuse vaccines will help bolster vaccine coverage rates, protecting the health of all Australians.