What evidence is required to be confident of natural immunity?
Patient history is often unreliable in terms of assessing natural immunity and physician-based clinical diagnosis is considerably less reliable than laboratory testing (via serology, polymerase chain reaction [PCR] or antigen detection). Vaccine preventable diseases such as measles, mumps, rubella and hepatitis B infection are now uncommon among children in Australia and other infections can have similar clinical presentations.
Testing for natural immunity
The AIR Immunisation Medical Exemption form has provisions for natural immunity to hepatitis B, measles, mumps, rubella and varicella viruses. If there is a history of pertussis or rarer conditions such as diphtheria, tetanus, meningococcal disease and polio, GPs should vaccinate the child rather than test serologically for immunity, because it is unclear if a satisfactory level of immunity is maintained following natural infection from these conditions. It may also be simpler to vaccinate for other conditions such as measles, mumps, rubella and varicella, as exemption to a combination vaccine is only possible if immunity is confirmed for all the antigens in the vaccine.
In some cases parents may request serological testing to see if their child has responded to previous doses of a vaccine. This is not recommended as a routine practice because immunity wanes after vaccination and serology results are dependent on the time post-vaccination that the sample is collected. A negative serology test may reflect waning immunity rather than non-response to the previous dose(s) of vaccine. It is safe to vaccinate a child who has pre-existing vaccine- or natural infection-induced immunity.
Identifying and managing concerns contributing to requests for vaccination exemption
As well as removing exemptions for ‘conscientious objections’, the no jab, no pay policy has also extended immunisation requirements for receipt of Federal Government family assistance payments to age 19 years on an annual basis (previously only at 1, 2 and 5 years of age). Although some parents of incompletely vaccinated children are happy to have them undergo catch-up vaccination, some have concerns, ranging from minor to major. Some parents, rather than having any philosophical opposition
to vaccination, will be concerned about vaccine safety due to previous adverse events in their child or in other family members, or will be concerned about what they have heard or read about vaccine safety. Some parents of incompletely vaccinated children are concerned about vaccine side effects and ‘toxic and harmful’ vaccine ingredients or have concerns that vaccines are ineffective and prefer ‘natural’ preventive approaches.
Leask and colleagues reported that parents can be divided into five different groups based on their vaccine concerns or acceptance.2
These five groups are:
- unquestioning acceptors
- cautious acceptors
- late or selective vaccinators