TUESDAY, Oct. 25 (HealthDay News) -- The most widely used flu
vaccine in the United States is only about 60 percent effective in
healthy adults, new research indicates.
That vaccine is the trivalent inactivated vaccine (TIV), which
accounts for about 90 percent of flu shots in this country,
according to a report in the Oct. 25 issue of
The Lancet Infectious Diseases.
The less common live attenuated influenza vaccine (LAIV) is 83
percent protective in children aged 7 and younger, but it's not
recommended for everyone in this age group.
The findings are in line with other recent reviews and don't
mean that people shouldn't get their annual flu shot, said Dr.
Joseph Bresee, chief of the epidemiology and prevention branch in
the influenza division of the U.S. Centers for Disease Control and
"The findings are not that unexpected, but flu vaccines do work. They don't work as well as we'd like them to work all the time, [but] flu is a bad disease. It can cause death and hospitalization, and the flu vaccine is absolutely the best tool to prevent that," Bresee said. "While we all want them to be better, they're still the best thing we have."
Since 2010, U.S. health authorities have recommended that all
individuals aged 6 months or older receive a flu vaccine, either
the traditional shot (this is the inactivated vaccine) or the
nasal-spray flu vaccine, which is made with live albeit weakened
influenza viruses. The nasal spray is only approved for people aged
2 through 49.
The inactivated vaccine has been in use since 1978, and
represents the lion's share of all influenza vaccines in the United
States. Only about 9 percent of vaccines are given in the live LAIV
form, which was approved for use in 2003.
One of the reasons the live vaccine is not used as much, despite
its greater effectiveness, is that it's only licensed for those
aged 2 to 49 and for those without underlying high-risk health
conditions, Bresee explained, which limits its use somewhat.
"I am sure that there may be other reasons for relatively little use, even among those eligible, but it is a good vaccine, and induces good protection for those eligible to receive it," he said.
The new meta-analysis included data from 31 previous studies on
the flu vaccine conducted over the past 40 years. The flu shot was
shown to be 59 percent effective in adults aged 18 to 65.
There were no trials in children 2 to 17 years old or adults
aged 65 and over.
The vaccine for the pandemic H1N1 flu was about 69 percent
effective, which the study authors said was "not adequate for a
"It's a classic glass-half-full, glass-half-empty situation," said Dr. John J. Treanor, a professor of medicine and of microbiology and immunology at the University of Rochester Medical Center in New York. "Almost every study they looked at showed some level of efficacy. Flu vaccines definitely work to prevent influenza. The argument is about just how effective are they."
But the study does "highlight the need for better flu vaccines,"
According to Treanor, there are several different vaccine
approaches scientists are researching.
One is just using a higher dose and, in fact, there is a
high-dose product on the market right now for seniors. The vaccine
does produce higher levels of antibodies, but it's not clear yet if
this translates into better protection against disease, Treanor
Another strategy is to make more potent adjuvants, which are
compounds added to vaccines to enhance their effectiveness.
U.S. Centers for Disease Control and
Prevention has more on the annual flu vaccine.
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