Moderna Inc.'s messenger RNA-based experimental seasonal flu vaccine has produced robust antibodies against all four strains of the influenza virus in an early stage study, the vaccine maker said on Friday.

The early-stage study is ongoing and a mid-stage study testing of the vaccine, mRNA-1010, is now fully enrolled, the company said.

This data, though limited, puts Moderna ahead of other drugmakers, including rival Pfizer Inc, that are also testing their flu vaccine based on messenger RNA.

Moderna also said it was developing a pan-respiratory annual booster vaccine, which would target multiple viruses including COVID-19, flu and respiratory syncytial virus.

The new vaccine, mRNA-1345, has demonstrated positive early-stage results, it said.

"Even before the COVID-19 pandemic, approximately three million people died each year due to respiratory infections ... our goal is to limit this suffering with an annual pan-respiratory single dose booster vaccine," Chief Executive Officer Stéphane Bancel said.