Key Points

• Invasive Haemophilus influenzae infections have been steadily increasing since the early 2000s. The highest incidence rates are observed among infants and the elderly.

• Non-capsulated strains are predominant among the elderly (85% of cases in 2025), whereas among children under 5 years of age, capsulated strains are more common, particularly serotype b (58% of cases in 2025) and serotype a (17% of cases in 2025).

• Hib vaccination has been mandatory for infants since 2018. Vaccination coverage for the three doses of hexavalent vaccines has been estimated at 96% by age 2 among children born between 2018 and 2021.

• Despite this high vaccination coverage, the number of cases of invasive Hib infection among children under 5 years of age increased during the 2018–2024 period.

• In 2025, the increase was even more pronounced, particularly starting in October 2025. The National Reference Center for Meningococcal and Haemophilus influenzae confirmed 62 cases of invasive Hib infections in children under 5 years of age in 2025, compared to 34 cases in 2024, representing an 82% increase. By comparison, in 2018–2019, fewer than 15 cases were reported each year.

• A slight increase has also been observed since 2020 for serotype a, although the number of cases remains lower than those for serotype b.

• The epidemiological situation shows that Hib continues to circulate at low levels in the population, with a marked seasonal pattern in the fall. The majority of cases of invasive Hib infections occur in children under one year of age, confirming the higher risk during the first year of life.

• The risk of severe Hib infection particularly affects infants in their first year of life who are unvaccinated or have not yet completed the vaccination schedule.

• As in previous years, and given the very high levels of vaccination coverage, the cases observed occurred mainly among children who were up to date on their vaccinations (84% of cases aged 6 to 11 months and 81% of cases aged 12 months and older). Thirteen vaccine failures were identified in 2025, but this represents a small number of events relative to the number of vaccinated children (approximately 5 events per 1 million vaccinated children).

• These data raise questions about current Hib vaccine immunity in children. They call for further studies to evaluate the efficacy and duration of protection of the currently recommended schedule for infants.