Haemophilus influenzae, babies and vaccination: these words keep coming up since serious infections caused by this bacterium rose sharply in France in 2025. Santé publique France, the French public health agency, recorded 62 cases of invasive Haemophilus influenzae type b (Hib) infection in children under 5, up from 34 in 2024. Babies under one year old account for 71% of these cases.
These figures come from the surveillance report published on 26 March 2026 by Santé publique France and the National Reference Centre for Meningococci and Haemophilus influenzae. The agency describes the rise as ‘unexpected’, more than 30 years after conjugate vaccines were introduced.
Haemophilus influenzae in babies: what is it?
Haemophilus influenzae is a bacterium and, despite its name, has nothing to do with the flu virus. It often lives in the throat without causing illness. It becomes dangerous when it gets into the blood or into the fluid surrounding the brain. This is known as an invasive infection.
There are several types. Type b, or Hib, is the most dangerous for young children: it can cause meningitis and blood infections. It is the one babies are vaccinated against. Other strains, known as non-encapsulated, mainly affect older people.
Of the 62 Hib cases in under-5s in 2025, the bacterium was found in the cerebrospinal fluid of 36 children, or 58%. This finding points to meningitis. It was found in the blood of 25 children and in a joint in one child.
The 2025 figures from Santé publique France
- 85 cases of invasive Hib infection in 2025 across all ages, compared with 42 to 57 cases a year between 2021 and 2024, and 20 to 23 cases a year between 2018 and 2020.
- 62 cases in children under 5, up from 34 in 2024. Before 2018-2019, fewer than 15 cases were reported each year in this age group.
- An incidence of 1.9 per 100,000 children under 5, compared with 1.0 in 2024.
- Three deaths reported in 2025: a baby under one month old, an 11-month-old and a 2-year-old.
Type b accounted for 58% of the invasive strains identified in under-5s in 2025. Type a accounted for 17%. No clusters were reported: cases were spread across the country, with 11 in Île-de-France and 10 in Auvergne-Rhône-Alpes.
A clear autumn peak
Hib keeps circulating ‘under the radar’, with a peak in autumn. Between October and December 2025, 28 cases were reported in under-5s, compared with 13 over the same period in 2023 and 10 in 2024.
Which babies are most affected?
The rise mainly concerns babies. Santé publique France compares 2025 with the average for 2022 to 2024.
- Under 6 months: 17 cases in 2025, compared with an average of 8.7.
- 6 to 11 months: 27 cases, compared with an average of 11.7.
- 1 to 4 years: 18 cases, compared with an average of 11.
The 6 to 11 months group saw the biggest increase. This is the period between the first two vaccine doses and the booster.
Were the affected babies vaccinated?
Yes, most of them. Vaccination status was known for 58 of the 62 children.
- Under 6 months, 14 of the 17 children had received one or two doses.
- Between 6 and 11 months, 21 of 25 children had received both doses.
- From 12 months, 13 of 16 children had received all three doses.
Santé publique France counts 13 vaccine failures in 2025, or about 5 per million vaccinated children. The average was 6 a year between 2018 and 2024. The agency points out that its data do not allow incidence to be compared by vaccination status.
The vaccine still works
These figures do not call the value of the vaccine into question. A study covering 2018-2024 puts its effectiveness at 91.2% in children aged 2 to 4 who had the full course. Coverage is high: 96% of children born between 2018 and 2021 had received three doses by the age of 2.
When almost all children are vaccinated, it is mathematically expected that most cases will occur in vaccinated children. What concerns the agency is the overall rise and the share of cases in 6 to 11-month-olds.
Will the infant vaccination schedule change?
Not for now. Since 2013, France has used a so-called ‘2+1’ schedule: one dose at 2 months, one at 4 months and a booster at 11 months. Before that, babies received three doses at 2, 3 and 4 months, then a booster at 16-18 months. Hib vaccination is compulsory in France for children born since 2018.
Santé publique France considers that these data ‘raise questions about children’s current vaccine immunity against Hib’. It calls for studies into the effectiveness and duration of protection of the current schedule. Several possible explanations are mentioned: the 2013 schedule change, carriage of the bacterium, an interaction with RSV. The report does not recommend any change to the schedule.
For parents, the message remains that of the baby vaccination schedule. Stick to the dates and don’t put off the 11-month booster. If the jab worries you, a few simple steps help ease vaccination pain in babies.
When to seek urgent medical help
An invasive Haemophilus influenzae infection progresses quickly. The signs are not specific to this bacterium: they are those of any serious infection in a baby. A fever in a baby under 3 months always needs prompt medical advice.
At any age, get medical help straight away if, along with the fever, your baby is unusually floppy, hard to wake or refusing feeds. The same applies to unusual crying, a grey complexion or spots on the skin. If in doubt, call the emergency services (15 in France). Our article on fever in babies explains the thresholds and warning signs in detail.
A trend seen in other invasive infections too
Hib is not the only bacterium being closely monitored. The 2025 report on meningococci, published by the same agency, also documents changes in severe infections in the very young. We summarised it in our article on meningococcus in babies.
Vaccinations are tracked through the compulsory check-ups of the first months. These can take place at the GP, the paediatrician or the PMI, France’s mother and child health service, as described in our article on the baby’s PMI appointment.
Key takeaways
- Invasive Haemophilus influenzae b infections in children under 5 rose from 34 cases in 2024 to 62 cases in 2025.
- Babies under one year old account for 71% of cases, with a sharp rise between 6 and 11 months.
- Most affected children were vaccinated for their age; the vaccine remains 91.2% effective after the full course.
- Santé publique France is calling for studies on the ‘2+1’ schedule, without recommending any change for now.
Sources
- Santé publique France, ‘Bilan de surveillance des infections invasives à Haemophilus influenzae en 2025’, national edition, A.-S. Barret, C. François, I. Parent du Châtelet (SpF), A.-E. Deghmane, M.-K. Taha (CNR des méningocoques et Haemophilus influenzae), published on 26 March 2026.
