Researchers say they’ve taken a major step toward developing a flu vaccine that works for multiple strains of the virus, thanks to a quirk of last year’s pandemic swine flu.

Most years, the seasonal flu virus morphs just a little, so vaccine makers have to guess what the strain will look like many months in advance. But last year’s novel H1N1 strain may change the game. Some of the antibodies that flu generates seem to be effective across many strains, and that could be the key to a universal vaccine.

“What the flu vaccine community would want would be antibodies that would provide immunity to all flus,” said Patrick Wilson, assistant professor of medicine at the University of Chicago. “Who knows? Maybe we have crossed the line – we’re getting closer.”

Wilson said some of the H1N1 antibodies target structures on the virus that hardly change from year to year. That means the flu bug couldn’t outsmart the shot by mutating, though he cautioned against underestimating the crafty virus. The results are published in the Journal of Experimental Medicine.