1. Definition and clinical relevance
- Immunisation is one of the most effective disease prevention tools available in clinical practice.
- Australia delivers mass immunisation through general practitioners, community nurses, and local government services using schedules based on National Health and Medical Research Council (NHMRC) recommendations, funded free of charge through the National Immunisation Program (NIP).
Why the childhood schedule matters:
- The developing immune system responds optimally to specific antigens at specific ages
- Timing and formulation are critical to vaccine effectiveness
Age-specific vaccine considerations:
- Conjugate vaccines (Hib and pneumococcal): protein-conjugated forms are much more effective than plain polysaccharide vaccines in children under 2 years
- Measles: vaccination delayed until 9 to 12 months because passively acquired maternal antibody neutralises the live attenuated vaccine virus before this age
- Rubella: given to all children (historically at 1 year and again at preschool age) to reduce circulating disease and protect against congenital rubella
Key clinical message:
- The benefits of immunisation greatly outweigh the risks of any adverse events
Documentation:
- Records entered into the Australian Immunisation Register (formerly Australian Childhood Immunisation Register)
- Managed through Medicare to remind parents when next dose is due and track completion of immunisation milestones
2. Key values, thresholds and decision rules
- The routine infant primary series uses a combination vaccine (DTPa-hepB-IPV-Hib) given at set schedule points.
- The Australian Immunisation Handbook is the definitive reference for exact ages and catch-up rules.
| Age / point | Vaccine(s) usually given | Notes |
|---|---|---|
| Birth | Hepatitis B (first dose) | Given on the day of birth as part of routine schedule |
| 2 months | DTPa-hepB-IPV-Hib | Can start as early as 6 weeks of age |
| 4 months | DTPa-hepB-IPV-Hib | Given even if first dose was at 6 weeks |
| 6 months | DTPa-hepB-IPV-Hib | Completes primary series |
| 12 months (first birthday) | MMR, meningococcal ACWY, pneumococcal conjugate (20vPCV) | "Second immunisation milestone" |
| 18 months | DTPa; Hib (4th dose) | Booster doses |
| 4 years | DTPa-IPV | Preschool booster |
| 11 to 13 years (adolescent) | dTpa; HPV; others per NIP | HPV historically recommended from age 9 to 26 years |
Key thresholds and decision rules:
| Rule | Detail |
|---|---|
| Hib schedule | 4-dose schedule at 2, 4, 6 and 18 months; first dose can be from 6 weeks |
| Tetanus principle | Multiple doses in childhood are required to reach a protective level of immunity |
| Interrupted schedule | Do NOT recommence from the start; do NOT add extra doses. Continue from where the child is up to |
| Live viral vaccines | MMR and OPV can be given on the same day; if different live vaccines cannot be co-administered they must be separated by at least 4 weeks |
| Adult tetanus booster | Recommended at age 50 if no booster in the past 10 years, given as dTpa to also cover pertussis |
| Egg allergy | Children with egg allergy CAN be immunised (routine childhood vaccines do not contain egg components); anaphylactoid reactions to egg warrant specialist immunisation clinic advice before MMR |
For the primary series there is no preferential recommendation between the two available hexavalent combination products (DT5aP-hepB-IPV-Hib(PRP-OMP) and DT3aP-hepB-IPV-Hib(PRP-TT)).
3. Approach: presentation and differential
Immunisation encounters are usually planned preventive-health visits, or arise opportunistically (for example, a newly arrived refugee, or a child presenting for another reason with an incomplete record).
History
- Review the immunisation record: doses received, dates and ages. Written records (including overseas and pre-departure records) are considered reliable evidence of vaccination status.
- Clarify prematurity and gestation (see Australian-specific considerations): a premature infant is still vaccinated by chronological age.
- Screen for contraindications and precautions: previous serious vaccine reaction, immunosuppression, current chemotherapy, allergy history (particularly anaphylaxis).
- Ask about egg allergy and, specifically, any anaphylactoid reaction to egg.
- In children from refugee-like backgrounds, take a verbal vaccination history but recognise the debate over the validity of parental or self-recall when no written record exists.
Examination
- Assess the child is well enough to vaccinate (minor intercurrent illness is not a contraindication).
- Check growth and development as part of the visit, and note any features suggesting immunosuppression.
- Identify a suitable injection site; in infants the anterolateral thigh is standard (combination vaccines are given into the lateral thigh).
Differential
The "differential" in immunisation practice is really a set of decisions:
- True contraindication versus false contraindication (for example, egg allergy is usually a false contraindication for routine vaccines).
- Immunosuppressed child: live vaccines (MMR) are contraindicated during chemotherapy; non-live vaccines can continue per the routine schedule.
- Catch-up versus routine: is the child on schedule, delayed, or with no documentation at all?
4. Investigations
Immunisation is largely a clinical activity; routine testing before catch-up is generally not required.
Bedside
- Confirm identity and record: cross-check against the Australian Immunisation Register.
- Document clearly which dose is being administered, for example "MMR dose 1 of 2," to support ongoing catch-up.
Bloods
- Routine serology against a range of vaccine-preventable diseases is not recommended to guide catch-up immunisation.
- Hepatitis B serology (infection and immunity) is part of initial health screening for people from refugee-like backgrounds.
- Targeted serology may be offered in specific situations, for example varicella serology if aged 14 years or older with no history of natural infection, and rubella serology in relevant groups.
Imaging
- No imaging is required for routine immunisation.
5. Management
Step 1: Deliver the routine schedule
- Administer the primary series (DTPa-hepB-IPV-Hib at 2, 4 and 6 months) with the first dose able to be given from 6 weeks of age.
- Give combination vaccines into the lateral thigh in infants.
- Proceed to the 12-month milestone (MMR, hepatitis B) and later boosters (DTPa at 18 months, DTPa-IPV at 4 years), then the adolescent doses (dTpa, HPV) per the NIP.
Step 2: Manage the interrupted or delayed schedule
- If a schedule is interrupted, do not restart and do not give additional doses.
- Continue from the point reached.
- Catch-up schedules for DTP, hepatitis B and Hib are set out in the Australian Immunisation Handbook.
Step 3: Catch-up immunisation
- Aim to immunise the child to a level equivalent to an Australian-born person of the same age.
- Complete, do not restart schedules where there is written documentation of prior doses.
- In the absence of written documentation, full catch-up immunisation is recommended.
- Respect vaccine age restrictions and consider any recent or pending schedule changes.
- Provide opportunistic immunisation where possible, but do not interrupt another provider's catch-up plan if one is already in place.
- Provide a written record and a clear ongoing plan, and enter details into the national register for children and young people under 20 years.
Step 4: Special populations
- During chemotherapy: live vaccines (MMR) are contraindicated; non-live vaccines can still be given per the routine schedule. After completion of chemotherapy, re-immunise following the routine schedule, generally starting 3 to 6 months after treatment ceases (immune recovery can begin as early as 3 months post-treatment).
- Egg allergy: routine childhood vaccines contain no egg components, so these children can be immunised; those with anaphylactoid reactions to egg should be assessed by a specialist immunisation clinic before MMR.
Step 5: Follow-up and completion
- Use the register to remind families when the next dose is due and to ensure milestones are met.
- Financial and provider incentives within Australia support timely, complete immunisation.
6. Australian-specific considerations
- The NIP provides schedule vaccines free of charge to all Australian children; the Commonwealth funds these while states and territories deliver programs.
- The Australian Immunisation Register (via Medicare) records doses for children and young people under 20 years and drives recall and incentive systems.
- Premature infants are vaccinated according to their chronological age, not corrected gestational age. A very preterm infant received hepatitis B at birth and, at 8 weeks (still equivalent to 34 weeks gestation), received DTPa, Hib and the second hepatitis B dose, with DTPa-HBV combination into the lateral thigh.
- Refugee and asylum-seeker health: almost all people arriving from refugee backgrounds need catch-up vaccination. Review all overseas and pre-departure records and update the Australian register. These groups are recognised as at increased risk of vaccine-preventable disease after arrival, and outbreaks linked to index cases have occurred.
- BCG is no longer given to all Australian children and is not part of the routine schedule.
- HPV vaccination is delivered through the school-based adolescent program and was recommended for the 9 to 26 year age group.
- The definitive Australian reference for all ages, intervals and catch-up algorithms is the Australian Immunisation Handbook.
Clinical pearls
- Never restart a schedule. An interrupted schedule is continued from where it left off; no extra doses are needed.
- Prematurity does not delay vaccination by chronological age. Preterm babies receive hepatitis B at birth and the primary series on time.
- Live vaccines rule: MMR and OPV can go on the same day; otherwise separate different live vaccines by at least 4 weeks.
- Egg allergy is usually a false contraindication for routine childhood vaccines; only true anaphylactoid egg reactions warrant specialist advice before MMR.
- Conjugate vaccines outperform polysaccharide in under-2s (Hib, pneumococcal), which is why the schedule uses conjugates in infancy.
- Written records trump recall: use documented overseas records to avoid unnecessary re-vaccination; with no documentation, give full catch-up.
- Do not use routine serology to plan catch-up, but do check hepatitis B status in refugee-background patients, and varicella or rubella serology in selected groups.
- After chemotherapy, resume the routine schedule around 3 to 6 months post-treatment; non-live vaccines can continue during treatment, live vaccines cannot.