Getting a flu shot is still the best way to guard against the flu, even though this year’s vaccine didn’t work for about 60 percent of the most prevalent strains. 

“Even in years like this, when the vaccine is not a perfect match, vaccination can result in the illness taking a milder form,” said Margaret Hessen, MD, an infectious disease specialist and Pennsylvania Medical Society member. 

The Food and Drug Administration is taking steps to make sure next year’s vaccine offers more protection by replacing all three flu strains used in the shot. It will include the Brisbane/10 strain, which caused the most sickness this year but surfaced too late to be included in the vaccine. 

The vaccine must be reformulated each year to keep pace with the quickly mutating virus. Normally, only one or two strains are changed, not all three. 

The government has created successful flu vaccines in 16 of the last 19 flu seasons. In those years, the shot offered about 70 to 90 percent protection from the flu, Dr. Hessen said. 

“The Centers for Disease Control and Prevention and the World Health Organization have done a good job of predicting strains in what is really a fluid, dynamic situation,” Dr. Hessen said. “The influenza virus is notorious for its ability to mutate.”