Officials have said the
worst may be over and flu cases are declining. The 2012-13 flu season
began in December, much earlier than usual, and was more severe than
last year's.
That particularly was
true for those 65 or older, according to a CDC report Thursday. The
vaccine was 9% effective in protecting people in that age group.
"One possible explanation
for this is that some older people did not mount an effective immune
response to the H3N2 component of this season's vaccine," the report
said. "However, it's not possible to say that for sure."
An H3N2 flu strain has been the most dominant and has been especially hard on the elderly.
Among those over 65, 146
per 100,000 were hospitalized for the flu virus, compared with a rate of
30 per 100,000 last year, the CDC said.
Dr. Thomas Frieden, the
CDC's director, said this month in a congressional hearing that about
twice as many elderly people have been hospitalized with flu symptoms
than in recent years. That includes the 2007-08 and 2003-04 seasons,
which also saw a predominant H3N2 strain.
"It seems that this
year's flu vaccine is not nearly as effective as we would like among
people over the age of 65 for one particular strain of flu," Frieden
said Thursday. "That's why early treatment is so important."
Officials maintained,
however, that those 65 and older should be vaccinated yearly, for
reasons including that this population is at high risk of serious
illness, hospitalization and death from the flu.
"This flu season has
been worse than average and particularly severe for the elderly,"
Frieden said.
"Although it's far from perfect, flu vaccination is by far
the best tool we have to protect from the flu."
Authorities earlier had
said the flu vaccine was 62% effective for adults and children. In the
Thursday report, the CDC revised that to 56%.
The new number, the
agency said, is "not significantly different" and continues to fall
within the confidence interval established earlier. But the lower number
includes an additional three weeks of data and was adjusted for various
factors, including age and race or ethnicity.
"Both estimates indicate
moderate vaccine effectiveness in preventing outpatient medical visits
due to circulating flu viruses in most of the population," the report
said.
In addition, while this
year's vaccine was considered a good match for the most common
circulating flu viruses, it only provided 47% protection against H3N2,
the main virus.
"We simply need a better
vaccine against influenza, one that works better and lasts longer,"
Frieden said. The Department of Health and Human Services as well as the
private sector are working on such a project, he said.
In addition, less than
half of school-age children -- the population mainly responsible for
spreading the flu virus -- got the flu shot, experts said. The CDC
recommends the vaccine for those 6 months of age and older.
According to the latest
numbers released Friday by the CDC, "influenza activity remained
elevated in the United States, but decreased in most areas."
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