Immunization coverage and timeliness of vaccination in young patients with inborn errors of metabolism: a French multicentric study.

Background: Inborn errors of metabolism (IEMs) are rare disorders that are heterogeneous in severity and clinical presentation. Patients with IEMs should receive the vaccination schedule recommended for the whole population, and specific vaccinations, such as the seasonal influenza vaccine, for the most vulnerable. The aim of this study was to evaluate vaccination coverage and timeliness in young patients with an IEM.

Patients & methods: We conducted a retrospective multicentric (7 centers) study between February 2021 and May 2022 evaluating vaccination coverage and delays in French young patients with an IEM according to the yearly French vaccination schedules published since 2002. The results were analyzed considering patient health conditions as stable or at risk (defined as cardiorespiratory failure or by an IEM with a serious risk of metabolic crisis).

Results: Two hundred seventy-five patients were enrolled in this study. Among them, only 164 (60%) were up-to-date with the standard French vaccination schedule, and 229 (83%) had received at least one vaccine from this schedule late. The rate of delayed vaccination was significantly greater in the at-risk group than in the stable group for the main primaries and first booster doses of the DTaP-IPV-Hib vaccine and for the first MMR injection. Finally, only 30 to 35% of at-risk patients were vaccinated against influenza during the three previous winters.

Conclusion: Young patients with an IEM had insufficient vaccination coverage with significant delays, exposing them to vaccine-preventable diseases, particularly at-risk patients with cardiorespiratory failure or a serious risk of metabolic crisis. Furthermore, only a few of the most vulnerable patients had received specific vaccinations, such as the influenza vaccine. Therefore, optimizing vaccination within the recommended schedule is crucial for this population of vulnerable children who have regular hospital follow-up.