ATLANTA -- The flu season is getting worse, and U.S. health officials say it's
partly because the flu vaccine doesn't protect against most of the spreading flu
bugs.
The flu shot is a good match for only about 40 percent of this year's flu
viruses, officials at the U.S. Centers for Disease Control and Prevention said
Friday.
The situation has even deteriorated since last week when the CDC said the
vaccine was protective against roughly half the circulating strains. In good
years, the vaccine can fend off 70 to 90 percent of flu bugs.
Infections from an unexpected strain have been booming, and now are the main
agent behind most of the nation's lab-confirmed flu cases, said Dr. Joe Bresee,
the CDC's chief of influenza epidemiology.
It's too soon to know whether this will prove to be a bad flu season overall,
but it's fair to say a lot of people are suffering at the moment. "Every area of
the country is experiencing lots of flu right now," Bresee said.
This week, 44 states reported widespread flu activity, up from 31 last week. The
number children who have died from the flu has risen to 10 since the flu
season's official Sept. 30 start.
Those numbers aren't considered alarming. Early February is the time of year
when flu cases tend to peak. The 10 pediatric deaths, though tragic, are about
the same number as was reported at this time in the last two flu seasons, Bresee
said.
The biggest surprise has been how poorly the vaccine has performed.
Each winter, experts try to predict which strains of flu will circulate so they
can develop an appropriate vaccine for the following season. They choose three
strains- two from the Type A family of influenza, and one from Type B.
Usually, the guesswork is pretty good: The vaccines have been a good match in 16
of the last 19 flu seasons, Bresee has said.
But the vaccine's Type B component turned out not to be a good match for the B
virus that has been most common this winter. And one of the Type A components
turned out to be poorly suited for the Type A H3N2/Brisbane-like strain that now
accounts for the largest portion of lab-confirmed cases.
Over the years, the H3N2 flu has tended to cause more deaths, Bresee said.
This week, the World Health Organization took the unusual step of recommending
that next season's flu vaccine have a completely different makeup from this
year's. The U.S. Food and Drug Administration is expected to make its decision
about the U.S. vaccine next week.
H3N2 strains are treatable by Tamiflu and other antiviral drugs, but the other,
H1N1 Type A strains are more resistant. Of all flu samples tested this year, 4.6
percent have been resistant to antiviral medications. That's up from fewer than
1 percent last year.
"This represents a real increase in resistance," Bresee said.
