Moderna’s mRNA-based flu vaccine showed mixed results in a Phase III trial, the company said Thursday.

The results from the safety and immunogenicity study showed the vaccine triggered an immune response for A strains of the influenza virus, but did not show the same level of efficacy for the B strains of the virus.

The vaccine, mRNA-1010, was tested in more than 6,000 adults over the age of 18 and showed greater effectiveness than existing vaccines for A/H3N2 and A/H1N1 strains in particular. However, it did not meet the same endpoints for influenza B/Victoria- and B/Yamagata-lineage strains.

Still, Moderna emphasized the efficacy for preventing the A strains, noting the elderly population is more vulnerable to those strains.

“We are encouraged by the safety and tolerability profile, and by the strong immunogenicity results against influenza A viruses which cause the overwhelming majority of flu-related diseases in older adults,” Moderna president Stephen Hoge said in a statement. “While we did not achieve non-inferiority for the influenza B strains which are more frequent in younger populations, we have already updated the vaccine that we believe could improve immune responses against influenza B and will seek to quickly confirm those improvements in an upcoming clinical study thanks to the agility of our mRNA platform.”

The news led to a drop in Moderna’s shares by 6%. The study did find, however, that mRNA-1010 was “generally well-tolerated,” the company said.

This is one of five flu vaccines Moderna currently has in its pipeline. Others, including mRNA-1011 and mRNA-1012, have “additional HA antigens” that aim to provide more coverage for the A strains.

The company is also exploring combination vaccines that can simultaneously offer protection against flu and respiratory syncytial virus (RSV), or flu and COVID-19. Those efforts come in the wake of the ‘tripledemic’ that hit the U.S. in the fall, in tandem with some of the highest levels of flu hospitalizations in years.

Notably, Moderna’s RSV vaccine received a Breakthrough Therapy Designation from the Food and Drug Administration at the end of January. 

“The goal of Moderna’s combination vaccine candidates is to provide protection against multiple respiratory pathogens in a single vaccine,” the company said.

Much of Moderna’s efforts to push forward on flu and combination candidates is to make up for the drop in revenue from its COVID-19 vaccine, now that demand has declined. “To fill that big COVID decline, you need RSV and flu,” Cowen analyst Tyler Van Buren told Reuters.

Moderna has also been doubling down on mRNA opportunities in general after it won big on its mRNA COVID-19 vaccine. 

Last year, it sought to raise awareness about its mRNA pipeline that includes candidates for immuno-oncology, rare disease, cardiovascular disease and autoimmune diseases.In December, Moderna also finalized a 10-year partnership with the U.K. government to build a new mRNA manufacturing facility to produce more vaccines.

This content was originally published here.