CDC Says Flu Vaccine Is 48% Effective against H3N2 Flu Strain This Year.

This year’s flu vaccine cut infection risk by less than half, according to federal data released Thursday.

Overall, the flu shot appears to be 48 percent effective, the Centers for Disease Control and Prevention published online in its Morbidity and Mortality Weekly Report.

The vaccine is generally 50 percent to 60 percent effective, according to the CDC.

“We’d like it to be a little higher,” said Dr. Richard Zimmerman, professor of family medicine at the University of Pittsburgh School of Medicine and Graduate School of Public Health. “In terms of respiratory hospitalizations, this season has been busy — not severe, but it has definitely not been light.”

Zimmerman runs the Pittsburgh arm of a group that studies flu vaccine effectiveness for the CDC, and he co-authored the recent CDC report.

He said the most common cause of influenza this year is the influenza A virus known as H3N2. That strain has led to most hospitalizations. The vaccine has been 43 percent effective against H3N2.

Comparatively, this year’s vaccine has been 73 percent effective in combating a so-called B strain of the virus.

“I’d say that vaccine has done moderately well against H3 and well against the B strain,” Zimmerman said.

The CDC’s findings are gathered through data from Nov. 28 through Feb. 4 for 3,144 children and adults who are enrolled in the U.S. Influenza Vaccine Effectiveness Network.

Last year at this time, the CDC said its vaccine was nearing 60 in efficacy rates, but by season’s end its effectiveness was 47 percent.

The CDC report comes as Pennsylvania’s flu activity begins to show signs of peaking, according to the state Department of Health.

State health officials cautioned residents to stay home when infected or consider vaccination if they skipped a shot this season.

“Some folks who aren’t feeling well may want to try and power through and go to school for that one test or go to work for that important meeting, but please stay home,” Dr. Loren Robinson, deputy secretary for health promotion and disease prevention at the state Department of Health, told the Tribune-Review on Thursday. “The flu is very transmissible from person to person.”

Pennsylvania reported widespread flu activity, meaning there are cases in each county, for the past eight consecutive weeks with no slowdown in sight. There have been 33,271 influenza cases and 51 flu-related deaths reported to the health department this season.

Last week, a 10-year-old Washington County girl, Payton Pierson, died of flu-related complications. It is still not publicly known whether she had a flu shot.

Nationally, the Centers for Disease Control and Prevention said that the 2016-2017 flu has reached epidemic levels, with widespread activity reported in 43 states.

There have been 2,878 reported influenza cases in Allegheny County and 984 in Westmoreland along with 506 in Butler County and 921 in Washington County.

“As long as the flu virus is circulating in a community, it’s not too late to get vaccinated,” Secretary of Health Karen Murphy said in a statement. “The flu shot is still the best way to make sure you and your loved ones are protected. Now that we are in peak flu season, make sure you’re taking steps to prevent getting sick with the virus.

“In addition to getting vaccinated, everyone should also practice common sense prevention methods like washing your hands often and staying home from school or work when you’re sick with the flu.”

The flu kills more than 30,000 people a year on average, with the young and the old being particularly vulnerable.

Overall, Robinson described this as an average flu season but said people still should take the virus seriously.

“We’re seeing the big peak right now,” she said.

The Tamiflu drug shortens the duration of symptoms but only when it’s taken within 72 hours of infection, Robinson said.

Before this flu season, experts wondered whether more children would avoid the vaccine because nasal sprays like FluMist are no longer available.

Many children preferred the mist to the shot because it’s not painful to receive, but officials have determined the spray to be ineffective.

Experts have said it’s still too early to measure whether the lack of nasal sprays led to a decline in pediatric vaccinations.