Interim data on flu vaccines estimate overall moderate protection in Europe and China

Estimates of current mid-season flu vaccine effectiveness (VE) in Europe and China range from 32% to 58% overall, with greater protection against influenza B than A, according to three studies published in Eurosurveillance.

32% to 58% protection in Europe

In Europe, the 2009 H1N1 influenza A strain is the predominant flu virus and is circulating along with influenza A(H3N2) and B/Victoria. 

Public health researchers who analyzed eight test-negative studies from 17 European countries (five single- and three multi-country) estimated an interim all-age influenza A VE of 32% to 53% in primary care from September 2024 to January 2025. In this setting, it was least effective among children and adults aged 65 years and older.

In hospitals, VE was 33% to 56%, with some signals of lower VE by subtype and higher VE against influenza B (58% or higher in both settings).

In summary, flu vaccination prevented one third to more than three quarters of infections in primary care or hospitals, but protection varied by age-group and study. The vaccine protected a third to over a half of participants against influenza A infection, the main circulating subtype.

The authors recommended continuing to promote vaccination among target groups and strengthening other prevention measures for older adults. They called for end-of-season studies with larger sample sizes and more information on virus characteristics that may help explain variations in effectiveness.