GSK touted Phase 3 data of its quadrivalent flu vaccine Fluarix Tetra. As a severe flu season continues to unfold in the U.S., GlaxoSmithKline is touting phase 3 study data showing its Fluarix Tetra can protect young children who are among the most vulnerable to the virus.

In children six to 35 months of age, Glaxo's vaccine was 63.2% effective against moderate-to-severe flu, and 49.8% effective against any flu, the company reported Tuesday, meeting its primary endpoint.

Investigators completed the work between October 2011 and December 2014 in 13 countries across Europe, Central America and Asia. In total, more than 12,000 children received either the GSK shot or a control vaccine.

When the flu vaccine was correctly matched with circulating strains, efficacy was higher at 77.6% against moderate-to-severe flu and 60% against any flu, the drugmaker reported.

Along with the elderly, pregnant women and people with certain chronic diseases, young children are at a higher risk for flu and related complications, making them a priority for annual influenza vaccination.

Still, the new study is the first randomized clinical trial testing efficacy for a quadrivalent flu vaccine in the age group, Thomas Breuer, Glaxo's chief medical officer for vaccines, said in a statement.

Breuer added that the study "adds to the growing body of evidence to support universal vaccination including all children from six months of age to help prevent influenza in this age group, as well as the spread of influenza across the community.”

Aside from efficacy, investigators found that vaccination with the GSK shot reduced doctor visits, antibiotic use and work leave for parents.

The results come as a severe flu season continues to wreak havoc in the U.S. and elsewhere, due in part to poor vaccine performance this year. According to an interim CDC report, flu vaccines have been just 36% effective at staving off the illness. Some studies and officials have suggested the egg-based production process is one reason for the performance.

Meanwhile, companies and health officials are increasingly looking to universal flu shots and cell-based production to improve on the status quo. Just last week, the National Institute for Allergy and Infectious Diseases presented a plan to develop a universal flu shot.  

GSK is among the companies to work on newer flu vaccines, having teamed with Valneva to develop candidates with the biotech's EB66 cell line.