Vaccination of immunocompromised children — formative SAQs

SAQ 1 (10 marks)

A four-month-old boy born overseas, now in Australia, is due for his routine immunisations. There is no newborn severe combined immunodeficiency (SCID) screening result on file. His maternal uncle died in infancy. He has persistent oral thrush and has crossed two weight centiles downward. His mother asks whether he can have his usual needles today. [1] [5]

a) State the single most important safety decision you must make before any vaccine is given today, and the specific group of vaccines that is at risk. (2 marks) [1]

b) List four features in this vignette that justify withholding live vaccines and investigating further. (2 marks) [5]

c) Name the live-attenuated vaccines that must be withheld today, and the test that confirms or excludes a combined T-cell defect. (3 marks) [1] [2]

d) Outline the management of the inactivated vaccines in this infant while the defect is being characterised, and the role of the household. (3 marks) [2]

SAQ 2 (10 marks)

A seven-year-old girl is two years post-haematopoietic stem cell transplant for aplastic anaemia. She is well, off immunosuppression, with no graft-versus-host disease and a normal recent lymphocyte subset. Her school is asking for her immunisation record. [1] [8]

a) Explain why her pre-transplant immunisation history cannot be relied upon, and what principle governs re-vaccination after transplant. (2 marks) [8]

b) Outline the re-vaccination schedule: which vaccines, in what order, and the rule that governs re-introduction of live vaccines. (4 marks) [1] [8]

c) Describe the role of post-vaccine serology, naming two antigens you would check and what you would do with a non-responder. (2 marks) [8]

d) Discuss how you would coordinate care between the transplant service, the general practitioner, and the school to prevent silent loss of coverage. (2 marks) [1]

Marking guide

SAQ 1. The key decision is the threat gate: a combined T-cell defect has not been excluded, so no live-attenuated vaccine may be given until it is. Withhold BCG, rotavirus, MMR, and varicella. The four features are the missing or unavailable newborn SCID screen, the family history of early male infant death, the persistent oral thrush, and the faltering growth. Confirm with the TREC newborn screen and lymphocyte subsets (T, B, and NK cells) with functional T-cell testing. Inactivated vaccines can proceed on schedule because they cannot replicate, and the household should be fully vaccinated (cocooning) while avoiding oral polio and live rotavirus in contacts. [1] [2] [5]

SAQ 2. Conditioning erases prior immunity, so the schedule must be rebuilt on evidence of reconstitution, not on a calendar date or the old record. Re-vaccinate with inactivated vaccines first (DTPa, IPV, Hib, hepatitis B, pneumococcal, inactivated influenza, meningococcal) from around three to six months post-transplant once reconstitution is documented, and re-introduce live vaccines (MMR, varicella) only after T-cell recovery is confirmed, typically around two years in the stable, graft-versus-host-disease-free child. Check serology for tetanus, pneumococcal, Hib, and hepatitis B, and re-vaccinate non-responders. Coordination requires a written, shared plan reconciled at every visit, with the school record updated and the transition explicitly handed over. [1] [8]