Madison, Wis.–based FluGen has announced that its Bris2007 M2SR flu vaccine candidate demonstrated protection against a multi-seasonal, seven-year drifted influenza strain in a Phase 2 study.

Some 54% of M2SR vaccine recipients were infected after exposure to a flu strain. Conversely, 71% of placebo recipients were infected, indicating that the vaccine was 24% effective against the strain.

The results, which were published in the Journal of Infectious Diseases, mark the first time a vaccine demonstrated the ability to protect against a highly drifted influenza A (H3N2) flu virus in a human challenge study, according to FluGen.

The study indicates that the vaccine triggers a broad immune response. Conversely, traditional flu vaccines offer strain-specific protection and struggle to protect against the H3N2 strain, which has driven an increasing proportion of flu cases in recent years.

In the challenge study, investigators randomized adults aged 18 to 55 to receive a single dose of either vaccine or placebo. Four weeks later, they were exposed to the H3N2 virus (A/Belgium/4217/2015) influenza strain. FluGen’s intranasal vaccine is based on the A/Brisbane/10/2007 strain.

A single dose of the vaccine induced neutralizing antibodies in 48% of recipients. Some 27% of recipients induced such antibodies in response to the challenge strain.