The companies said they plan to start a late-stage trial in the coming months.

"This vaccine has the potential to lessen the impact of two respiratory diseases with a single injection and may simplify immunization practices," Pfizer’s head of vaccine research and development, said in a statement.

The data from the trial showed that the flu-COVID vaccine demonstrated robust immune responses to influenza A, influenza B and SARS-CoV-2 strains, the companies said.