The role of the Immunisation Adverse Events Clinic at The Children's Hospital at Westmead

Adverse events following immunisation: Prospective cohort study evaluating Australian children presenting to specialist immunisation clinics

OBJECTIVE

Prior experience of an adverse event following immunisation is a known barrier to vaccination. Limited Australian data evaluating adverse event recurrence among children exists to inform clinical decisions. We aimed to assess adverse event following immunisation recurrence among children with prior adverse events and to evaluate if family history increased adverse event risk.

METHODS

A prospective cohort study was conducted from March 3rd until August 18th, 2023. Children ≤ 16 years with prior adverse events following immunisation in themselves or family were recruited from specialist immunisation clinics at two quaternary paediatric hospitals. Adverse event outcomes were collected via surveys administered at presentation, three, and eight days post vaccination, and analysed by key characteristics and potential risk factors.

RESULTS

Forty three of forty nine (43/49, 87.8 %) children enrolled received further vaccines. Of those who completed the follow up surveys, 50.0 % (16/32) reported an adverse event. Recurrence of prior adverse events occurred for 23.3 % (10/43, 95 % CI: 11.8 % - 38.6 %) of the cohort. Two of twelve (2/12, 16.7 %) participants with prior serious adverse events who received further vaccines reported a serious adverse event recurrence. No post review serious adverse events were observed in children with prior non serious adverse events. Neurological conditions were a risk factor for prior (neurological condition 3/3 versus no neurological condition 2/40, p < 0.001) and post review (neurological condition 2/3 versus no neurological condition 0/28, p = 0.006) post vaccination seizures. Family history had no relationship to post review adverse events (family history 5/8 versus no family history 11/23, p = 0.685).

CONCLUSION

Revaccination is safe for the majority of children with a personal or family history of adverse event following immunisation.

Vaccination uptake by vaccine-hesitant parents attending a specialist immunization clinic in Australia

Vaccine hesitancy (VH) is an issue of global concern. The quality of communication between healthcare providers and parents can influence parental immunization acceptance. We aimed to describe immunization uptake following specialist immunization clinic (SIC) consultation for Australian children of VH parents as a cohort, and according to pre-clinic parental position on immunization. At a single tertiary pediatric SIC (RCH, Melbourne) a retrospective descriptive study classified VH families according to 3 proposed parental positions on immunization at initial clinic attendance. Immunization status at follow up was ascertained via the Australian Children's Immunization Register and National HPV Program Register and compared between groups. Of the VH cohort, 13/38 (34%) families were classified as hesitant, 21 (55%) as late/selective vaccinators and 4 (11%) as vaccine refusers. Mean follow up post-SIC attendance was 14.5 months. For the overall VH cohort, the majority chose selective immunization (42%) following SIC consultation. When analyzed by pre-clinic parental position on immunization, there was a trend for hesitant families to proceed with full immunization, selective families to continue selective immunization and refusing families to remain unimmunised (p < 0.0001). The most commonly omitted vaccines were hepatitis B (66%) and Haemophilus influenzae type B (55%), followed by the meningococcal C conjugate vaccine (53%) and measles, mumps and rubella vaccine (53%). Immunization outcome appears to correlate with pre-clinic parental position on immunization for the majority of families attending a SIC in Australia, with selective immunization the most common outcome. Tailored communication approaches based on parental position on immunization may optimise clinic resources and engagement of families, but require prospective research evaluation.