Overall, across the age groups studied, the vaccine's effectiveness was found to be a moderate 56 percent, which means those who got a shot have a 56 percent lower chance of winding up at the doctor with the flu. That is somewhat worse than what has been seen in other years.
For those 65 and older, the vaccine was only 27 percent effective against the three strains it is designed to protect against, the worst level in about a decade. It did a particularly poor job against the tough strain that is causing more than three-quarters of the illnesses this year.
It is well known that flu vaccine tends to protect younger people better than older ones. Elderly people have weaker immune systems that don't respond as well to flu shots, and they are more vulnerable to the illness and its complications, including pneumonia.
But health officials said they don't know why this year's vaccine did so poorly in that age group
The CDC's Bresee said there is a danger in providing preliminary results because it may result in people doubting — or skipping — flu shots. But the figures were released to warn older people who got shots that they may still get sick and shouldn't ignore any serious flu-like symptoms, he said.
you won't like have a bad reactions to the shot, either.