This year‘s flu vaccine may not be good enough to keep you out of the doctor‘s office but it remains the best defense against a strain that‘s circulating in western Pennsylvania, health authorities said Friday.

A nationwide study partly conducted in Pittsburgh concluded the current vaccine is 62 percent effective, which is line with the vaccine‘s effectiveness in prior years, according to the Centers for Disease Control and Prevention.

“The flu vaccine is far from perfect but it‘s still by far the best tool we have to prevent the flu,” said Dr. Tom Frieden, the CDC‘s director. “Childhood vaccines get 90 percent efficacy and that‘s what we‘d like to see.”

In explaining the vaccine‘s power, Frieden said people who receive it are 62 percent less likely to require a doctor‘s checkup or hospitalization. In the past, vaccine effectiveness has ranged anywhere between 50 and 70 percent, he said.

Changes in the influenza strains circulating from year to year make it more difficult for scientists to deliver a better vaccine, said Dr. Richard Zimmerman, professor of family medicine at the University of Pittsburgh School of Medicine. The vaccine typically contains a mix of flu viruses.

“It‘s hard to come up with a more effective vaccine because the flu changes all the time,” Zimmerman said. “The challenge is that you have to keep making a new vaccine each year.”

UPMC and the University of Pittsburgh‘s Schools of the Health Sciences are one of five national sites that studied the vaccine‘s effectiveness as part of the U.S. Flu Vaccine Effectiveness Network. There were 251 local participants with acute respiratory illnesses, the most from all the sites, which collected specimens and analyzed data from 1,155 people.

Zimmerman said 83 of the 251 local participants had the A strain of the virus that causes more severe symptoms.

“It‘s been a fairly severe season in this region at this point,” he said. While B strains of the virus have not been as prevalent in this region, Zimmerman said that may change as the season progresses. Current flu shots, which authorities estimate have been given to about 130 million people, contain vaccines against that strain.

The CDC‘s Frieden said the flu is likely to continue for several weeks.

This article was written by Channel 11’s news exchange partners at TribLIVE.