The jury is still out on the Turnbull government's landmark No Jab No Pay policy, with immunisation experts warning policies targeting vaccine refusers may have unintended consequences.
Australia's vaccination rates are relatively high and at least comparable with similar developed countries, said researchers at the National Centre for Immunisation Research and Surveillance.
Parents who actively refuse to vaccinate their children were on the "extreme end" and a small proportion of the remaining 7 per cent of the population, they wrote on Monday in the Medical Journal of Australia.
Their recent study estimated just 3.3 per cent of children between one and six years old had parents who were vaccine objectors, both registered and unregistered in 2013.
The threat of disease transmission posed by vaccine refusers is low, the MJA perspective piece read.
"Vaccine refusal is only one of a range of factors relevant to further improvements in vaccine coverage and disease control,"said the immunisation experts including Professor Peter McIntyre at the Childrens Hospital Westmead and Professor Julie Leask at the University of Sydney's School of Public Health.
Children miss vaccinations for a range of reasons, often closely linked to socio-economic hardship and logistical barriers.
Though there have been consistent geographic clusters of objectors, the highest (about 10 per cent) in regional areas of northern NSW and south east Queensland, the national childhood immunisation rate currently sits at 93 per cent and has remained over 90 per cent for more than 15 years.
Any policy response designed to protect the public from the threat of infectious diseases needed to be proportionate, the researchers argued.
The federal government's landmark No Jab No Pay policy must be rigorously scrutinised in order to identify the benefits of the program as well as any unintended adverse impacts it may have for the children of vaccine-refusers as well as those who may miss out for other reasons.
The legislation was introduced nationally on January 1 and removed the exemption that had previously allowed parents whose children were not fully vaccinated to remain eligible for family assistance payments if a health practitioner certified that they were conscientious objectors.
The Victorian No Jab, No Play legislation requires children to be fully immunised to attend childcare centres unless they have an approved medical exemption or they are on a catch-up schedule.
The highly restrictive policy could unintentionally cut off access to important early childhood education for some children, the researchers said.
NSW currently allows a written exemption for children of vaccine-refusing parents.
The additional protection the community can expect from excluding these children from childcare and preschool may be negligible.
For instance, whooping cough (pertussis) "Although highly effective against severe disease, acellular pertussis vaccines give lower (71-78 per cent) protection against mild disease so even if 100 per cent of children were fully vaccinated against pertussis some children would still contract mild disease if exposed," the researchers wrote.
"This would not generate strong herd immunity comparable to high coverage of measles vaccine," they said.
The most effective method of boosting vaccine rates will likely be implementing measures that are already proven to improve access and minimise logistic barriers to vaccination for children and their families, Professor McIntyre and his colleagues advised.
They also advocated well-structure research and evaluation of the government's policy and any new intervention that aims to address refusal and hesitancy among parents.
They welcomed the latest budget's allocation of funding to measures for enhancing communication about and access to vaccines.
