Key Points

• The 2021–2022 influenza epidemic was short-lived (8 weeks), but was preceded by a long pre-epidemic alert phase from 2021-S51 to 2022-S08, followed by late circulation of the influenza virus compared to previous winter seasons.

• Co-circulation of the A(H3N2) and A(H1N1)pdm09 viruses.

• Epidemic peak observed between weeks 2022-S11 and 2022-S14 according to indicators.

• Moderate to high impact of the epidemic on outpatient care.

• Moderate impact on hospital care (emergency department visits, hospitalizations, and intensive care admissions).

• Few reports of clusters of acute respiratory infections in elderly care facilities.

• Flu mortality is difficult to compare with previous seasons due to the co-circulation of SARS-CoV-2.

• Children and young adults particularly affected by the influenza epidemic.

• Older adults relatively spared.

• Vaccination coverage in at-risk groups (56.8%) increased compared to the 2019–2020 season but remains below the 75% target.

• The 2021-2022 winter season was marked by changes in all epidemiological surveillance systems and indicators, the co-circulation of the COVID-19 virus, and the implementation of preventive measures and isolation protocols. All of these changes have altered both the natural course of the influenza epidemic in Brittany and the methods used to describe it.