Giving mice a special nasal spray meant to protect against whooping cough also helps them survive a flu infection better—not by killing the flu virus, but by calming down their overactive immune response, which otherwise causes dangerous lung swelling.

When mice get a special nose spray vaccine called BPZE1, it helps them survive a dangerous bacterial lung infection by calming down their immune system’s overreaction—especially by stopping too many inflammation cells from rushing in and by bringing in peacekeeping immune cells that keep things from getting out of hand.