Changes in Post-Transplant Vaccine Coverage After Implementing Structured Vaccine Reviews in Pediatric Solid Organ Transplant Recipients in British Columbia, Canada: A Canadian Immunization Research Network Study

Children with solid organ transplants (SOT) are at increased risk of infections but may be under-vaccinated. In 2021, our center implemented structured post-SOT vaccine reviews. We conducted a single-center, pre-post observational study with a repeated cross-sectional design to assess changes in vaccine coverage from 2020 to 2024.

We performed a chart review of SOT recipients aged 2-18 years who were ≥ 1 year post-transplant and followed at our clinic on March 1, 2020, and/or March 1, 2024. Patients eligible at both time points (repeat participants) were included in both cohorts; those eligible once (single-time-point participants) were included in the respective cohort. We assessed individual and overall vaccine coverage, defined as receipt of all recommended non-live, non-seasonal vaccines. Comparisons used the chi-square and paired McNemar's test (two-sided p < 0.05).

Overall vaccine coverage increased from 33% in 2020 to 51% in 2024. The most prominent changes were observed for 23-valent pneumococcal polysaccharide (PPV23) and human papillomavirus (HPV) vaccines, with significant improvements among both single-time-point (PPV23: 58%-88%, p < 0.001; HPV: 32%-81%, p = 0.003) and repeat participants (PPV23: 52%-76%, p = 0.008; HPV: 20%-53%, p = 0.008). Overall vaccine coverage among patients transplanted at age < 2 years was significantly lower compared to older children in 2020 but not in 2024.

Structured post-transplant vaccine reviews were associated with an increase in coverage across most vaccines and all organ subgroups, supporting its integration into routine post-transplant care and prospective, multicenter evaluation.