Flu shot only 36 percent effective at stopping virus this year

It’s still better than none, CDC insists

NEW YORK — The flu vaccine is doing a poor job protecting older Americans and others against the bug that’s causing most illnesses.

Preliminary figures released Thursday suggest the vaccine is 36 percent effective overall in preventing flu illness severe enough to send a patient to the doctor’s office.

There’s only been one other time in the last decade when the flu vaccine did a worse job.

Still, the Centers for Disease Control and Prevention report that while this year’s flu shot is far from perfect, it’s certainly better than nothing because it offers some protection, especially against other strains that are just starting to emerge.

The CDC report on the vaccine’s midseason effectiveness confirms what federal health officials and infectiousdisease experts have suspected for some time. In unrelentingly bad flu seasons such as the current one, which is dominated by the most dreaded flu strain, vaccines are less effective.

Most illnesses this winter have been caused by a nasty kind of flu called Type A H3N2. The vaccine was only 25 percent effective against that type.

H3N2 tends to cause more suffering and have been responsible for the worst recent flu seasons. But experts have wondered whether low vaccine effectiveness is another reason for the surprisingly severe season hitting the United States this winter.

Based on these numbers, the answer is yes.

“The fact that the vaccine doesn’t work as well as we would like is clearly a contributing factor,” said William Schaffner, a Vanderbilt University vaccine expert.

The numbers are a snapshot taken in the middle of a frantic flu season. They are based on relatively small numbers of people and they are considered preliminary. Numbers may change as the season continues and more patients are added to the study.

And experts say it’s still worth getting a flu shot. It still provides some protection, it can lessen the illness’s severity, keep people out of the hospital and save lives. There are as many as 56,000 deaths connected to the flu during a bad year.

“Any type of vaccine is better than none,” said Scott Hensley, a University of Pennsylvania microbiologist who has led studies that raised critical questions about the vaccine.

The effectiveness estimates come from the tracking of about 4,600 children and adult patients in five states. To make the effectiveness calculations, researchers tracked who got the flu, and who among them had been vaccinated.

The vaccine provided good protection — 67 percent effective — against another common kind of flu virus, Type A H1N1, which has not been seen much this winter. And it was 42 percent effective against Type B flu viruses.

The effectiveness of the American flu shot appears to vary with age. For instance, it reduced the risk of getting a serious case of any type of flu by 59 percent among children ages 6 months through 8 years. (The vaccine isn’t recommended for infants younger than 6 months of age.) For adults between the ages of 18 and 49, it reduced the risk of a serious flu by 33 percent.

Seasons when this flu bug is dominant are associated with more severe complications, especially for people older than 65, young children and others with certain chronic conditions. If the preliminary numbers hold, it will mean that in five of the last eight flu seasons, vaccine was essentially ineffective in seniors.