That wasn't anyone's fault really. Vaccines take months to make, and flu viruses are constantly mutating, so making the shots takes some guesswork. But what if doctors had a universal flu vaccine—one that worked for multiple years across multiple strains? Two new studies take them a small closer to that goal.

Today, independent teams reported in Science and Nature Medicine how they've tinkered with a piece of viral protein so it can teach immune systems—in this case, in mice, ferrets, and monkeys—to fight whole groups of viruses rather than just a single strain. "It's a great first step in the road for generating a universal flu vaccine," says Gary Nabel, who oversaw one of the studies as former head of the National Institutes of Health's Vaccine Research Center.