Background

This guideline provides technical detail on an abridged catch-up schedule (ACS) for adolescents - using Infanrix Hexa^® (DTPa-IPV-Hep B-Hib) and Priorix tetra^® (MMR-V) up to the age of 18 years. The ACS effectively halves the number of vaccinations required for catch-up in adolescents, provides a uniform dosing schedule, and simplifies catch-up planning.

The ACS has been used at RCH for more than three years, and is recommended in European guidelines for catch-up immunisation in paediatric oncology patients. The ACS has been implemented in PRIME (Program for Refugee Immunisation Monitoring and Education) in the City of Greater Dandenong (CGD) from 2022. This pilot was endorsed by the Vaccine Safety Committee, Immunisation Section, Department of Health in November 2021, and approved by the the Chief Health Officer (CHO) in January 2022. CHO approval has since been extended to other PRIME local government sites in Whittlesea, Hume and Casey until end of 2023. This guideline is intended for PRIME partners and the RCH Immigrant health service, use of the ACS has not been approved more broadly in Victoria.

Abridged catch-up schedule for age 10 years and older

Table 1 shows a comparison of the standard and abridged vaccination schedule. Key differences in the ACS are the use of:

• Infanrix Hexa^® vaccine (instead of separate dTpa, Hep B and IPV vaccines) in adolescents aged 10-17 years 
• Priorix-tetra^® (MMR-V instead of separate MMR and VV vaccines) in adolescents 15-17 years. 

This regimen differs from current recommendations within the Australian Immunisation Handbook for the use of Infanrix Hexa^® (DTPa-IPV-Hep B-Hib) and MMR-V vaccine . 

Table 1: Comparison of the standard and abridged catch-up vaccination schedule for age 10 years and older

_{Note: In early 2023, HPV dosing changed to single dose schedule immunocompetent age 9-26 years - this further simplifies catch-up vaccination so 3 visits can be completed over 4 months.} 

Planning and administering abridged catch-up schedule

Ensure all previous vaccinations are recorded on AIR.

• For many years overseas records were uncommon, however recent Afghan and Ukrainian cohorts have often had written vaccination records. Use calendar converters as required - e.g.  Afghan
• Offshore immigration medical examinations (IME) now include a broader range of vaccinations, and may include overseas vaccine records - check  HAPlite and also record these vaccinations on AIR.
• Always ask families if they have had other vaccines in Australia - in practise we often see situations where vaccines have not been entered on to AIR.   
  

Include prior vaccines in catch-up planning

• Documented overseas vaccinations or partial vaccinations in Australia should be factored into catch-up planning.   
  

Consider serology

• Post-arrival refugee health screening includes HBV serology (all ages), varicella serology (14 years and older) and rubella serology (females childbearing age), although available evidence suggests screening coverage is very poor for children/adolescents in Victoria (<5% outside specialist services). It is clinically reasonable to vaccinate without serology in adolescents.
  
• Positive serology can facilitate an 'exemption due to immunity' on AIR and reduce the number of catch-up vaccinations. While routine serology for vaccine preventable diseases (VPD) is not recommended in refugee screening guidelines, if it has been completed (e.g. MMR-V serology) this should be included in planning.
• If an adolescent has HBV immunity, but still requires dTpa and polio vaccinations, or, if screening if not available, it is clinically reasonable to offer hexa as a combined vaccine.
• Where adolescents have had their d-T containing vaccines and still require HBV vaccination and/or polio vaccination, use individual vaccines if further doses of d-T are not required.
  
• MMR-V serology - for non-immune adolescents aged 14 years and older, 2 doses varicella required - given as MMR-V x 2. If no serology available, suggest MMR-V x 2. Varicella immune adolescents aged 14 years and older would therefore only require MMR x 2, and age <14 years require MMR-V x 1 and MMR x 1.
  

Vaccine intervals  

• For children aged 10 years and older with no prior vaccinations, catch-up vaccination can be completed in 3 visits over 4 months. Children aged 5-9 years require a fourth visit 6 months after the primary series to provide a fourth dose of DTPa. See Table 2. 
• We suggest using defined intervals for all ages (5-17 years) to simplify planning and delivery - this also means siblings can be vaccinated concurrently at school based visits.  
  

Other

• Obtain informed consent for ACS, working with interpreters as required and ensuring families understand vaccines, visits, and follow up.  Please follow site guidelines and available resources.  
• Due-overdue rules and Centrelink payments are no longer a concern with the reduction to single dose HPV and 4-month duration of catch-up - catch-up on AIR can be checked at the 1^st visit. 
• Vaccine selection - Hexa and priorix have been used as they do not contain porcine gelatin, although all vaccine formulations are acceptable (see Resources). Nimenrix (MenACWY) has also been used to reduce vaccine doses. 
• Include (seasonal) flu vaccine and covid vaccine wherever possible. 
• Consider medical conditions requiring extra vaccine protection - see including asplenia, HIV infection/other immunosuppression, severe or chronic medical conditions, cochlear implants/CNS shunts - additional pneumococcal vaccines, hepatitis B or hepatitis C (where hepatitis A vaccination is recommended in the absence of immunity).
• Consider pregnancy in all females of child bearing age, including in adolescents. In general LAV (MMR, MMR-V, VV) and HPV are contraindicated during pregnancy, and should not be given for 28 days prior to pregnancy.
  

Table 2: Full catch-up vaccination for age 5-17 years (using the ACS for 10-17 years)

_{Note: Check catch-up vaccination at 1st visit on AIR - HPV changes have simplified planning so 3 visits can be completed over 4 months - within the 6-month window for catch-up. Use Nimenrix for MenACWY vaccination so only single dosing is required.} 

To date, the CGD pilot of the ACS has demonstrated high uptake, few side effects ( <10% students reporting any concern, which is much lower than expected as per Immunisation handbook) and very positive reception from students and staff (less distress, fewer vaccines, quicker and easier administration). The PRIME teams would welcome feedback on this guideline. 

Resources

• MVEC - Porcine gelatin and vaccines 
• Queensland health - medicines/pharmaceuticals of animal origin

_{Immigrant health clinic resources. Author: Georgie Paxton, March 2023. Contact: georgia.paxton@rch.org.au}