Novavax announced that its Covid-flu vaccine triggered an immune response similar to its stand-alone shots.

Chief Medical Officer Filip Dubovsky, during a call with reporters, said the company’s early phase clinical trial found that up to 25 micrograms of the Covid formulation combined with up to 35 micrograms of the flu formulation triggered a promising level of protective antibodies.

“What we demonstrated in this study is we were able to get the immune responses really comparable to what the individual vaccines did prior to combination,” Dubovsky said.

Participants in the phase one trial had a median age of 59 and all of them had previously received Covid vaccines. Novavax is presenting the data at the World Vaccine Congress in Washington, D.C., on Wednesday.

Novavax plans to move forward with a phase two trial this year to confirm the appropriate dosing levels, and launch a phase three trial on efficacy during the 2023 flu season at the earliest, Dubovsky said.

Public health experts expect Covid to become a seasonal respiratory virus similar to the flu that will likely require annual vaccination because immunity from the shots wanes over time. The vaccine makers are racing to develop combination shots targeting both viruses to make it easier for people to get protected when Covid and the flu are circulating simultaneously. “Combination vaccines are an attractive public health intervention,” Dubovsky said. “You are hitting two life-threatening diseases in one medical contact, giving a single vaccination.”

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