Since 2022, a resurgence of invasive Haemophilus influenzae infections has been observed in the EPIBAC network, as has been the case with other respiratory-transmitted bacterial infections.

Among children under 5 years of age, the number of cases of invasive Hib infections confirmed by the National Reference Center for Meningococcal and Haemophilus influenzae Diseases has increased since 2018. It rose from 14 cases in 2018 to 46 cases in 2021, then decreased in 2022 and 2023 before rising again in 2024 and 2025. According to NRC data, 62 cases of invasive Hib infection were identified in 2025.

A retrospective analysis of cases caused by serotype b that occurred between 2018 and 2024 showed that the majority of cases were up to date on their vaccinations, but that the estimated vaccine efficacy of the full vaccination series remained high, at over 90%.

Vaccine failures remain very rare compared to the number of children vaccinated, but these data raise questions about risk factors that may impact vaccine efficacy, the vaccine’s effectiveness in reducing carriage and transmission of the bacterium in the population, and finally, the duration of protection provided by the current vaccination schedule.