before a 2 dose Swine Flu vaccine can be effective.
August 26, 2009
Experts answer questions about flu vaccines
The novel H1N1 flu strain, commonly known as swine flu, circling the
globe has prompted the U.S. government to order 195 million doses of
vaccine and prepare for a widespread vaccination campaign that would
be carried out along with the already scheduled effort to vaccinate
people against seasonal flu. USA Today reporter Steve Sternberg asked
vaccine experts to address questions about the pandemic vaccination
program and the vaccine.
Q: What makes the new flu vaccine different from seasonal vaccines?
A: The regular flu vaccine always has three different influenza
viruses in it, says Baylor College of Medicine vaccine expert Carol
Baker, a member of the government's Advisory Committee on Immunization
Practices (ACIP). That's both the nose spray vaccine and the
injectable vaccine. The three strains are the ones that are going to
be around in the fall and winter, she says. The H1N1 vaccine will be
made of one virus.
Q: How many shots will people need?
A: Seasonal vaccine can be given in a single dose, Baker says. That's
because the three strains in the seasonal vaccine have been around for
awhile and most people have been exposed to them, she says. Once
you're exposed to a virus, your immune system is primed to fight it
off once it turns up again. Vaccine ramps up that protection. Children
under 9, who have never received the flu shot before, typically need
two doses of seasonal vaccine, according to the American Academy of
Q: What about the swine flu pandemic vaccine?
A: We anticipate that everybody's going to need two doses of the
pandemic vaccine, Baker says. That's because the swine flu virus is so
different from typical viruses that very few people - except maybe the
elderly, who have been around longer and may have encountered a virus
like it - have been exposed to it, she says. That makes most of us
like children, lacking immunity and needing a booster dose.
Q: Who should get vaccinated for seasonal flu? What about pandemic
A: Seasonal flu vaccine campaigns usually focus on the elderly and
people of all ages with chronic diseases that can put them at higher
risk of potentially dangerous complications, Baker says. Pandemic flu
is striking a much younger population, including pregnant women, so
the ACIP recommended that it be given to pregnant women, people who
live with or care for children younger than 6 months old, health care
workers, people ages 6 months to 24 years and people 25 to 64 who have
chronic illnesses or immune problems.
Q: How long will it take for the vaccine to provide protection?
A: At least a month, because the two shots will come a week apart and
the immune system will not be fully armed until a week or so after
that booster shot, Baker says.
Q: Is the vaccine safe?
A: It's expected that it will be just as safe as seasonal flu vaccine,
Baker says. It's a new vaccine, so she understands why some people
worry about safety, but as a vaccine expert she doesn't share that
concern, she says. Each year, the strains in the old vaccine are
swapped for new strains, and there have never been problems, other
than the usual side effects of minor fever, aches, pains and soreness
at the injection site.
Q: What about thimerosal? Is that safe?
A: Thimerosal is a preservative used in vaccines. People worry about
thimerosal because it's a form of mercury, which can be toxic,
especially for pregnant women and young children, Baker says. What
complicates things more is that pregnant women are considered a
priority group for vaccination, because their death rate has hovered
around 6%. But thimerosal, made of ethyl mercury, is different from
the methyl mercury found in fish, she says. Methyl mercury can cause
congenital problems in fetuses. The ethyl mercury used in vaccine
isn't thought to pose a problem, especially because it's used in trace
Q: I've heard researchers may need to use an immune booster, called an
adjuvant, for flu vaccine. What's that?
A: For reasons that aren't clearly understood, certain substances
significantly increase the potency of vaccines, says immunologist
Philippa Marrack of National Jewish Health in Denver. These adjuvants,
as they're known, are widely used in children's vaccines, and they're
a reason why measles, mumps, rubella and diphtheria vaccine work as
effectively as they do, Marrack says. Adjuvants aren't typically used
in flu vaccines in the USA, though they are in Europe, she says.
Adjuvants boost potency, lower the cost of vaccination and make
vaccines more widely available.
Because researchers are concerned about the potency of the H1N1
pandemic flu vaccine, they've begun testing versions made with
adjuvants. Canada has gone even further, buying millions of doses of a
vaccine-adjuvant combination from GlaxoSmithKline. Tests of adjuvanted
flu vaccine in the USA probably will begin soon, says Anthony Fauci,
director of the National Institute of Allergy and Infectious Diseases.
U.S. public health authorities have been reluctant to use adjuvants in
flu vaccine in the past because they don't want concerns about their
safety to stand in the way of persuading people to get the vaccine.
Q: When will the vaccine be available?
A: Studies have just begun to determine the dose and to make sure the
vaccine is safe. Jesse Goodman, deputy commissioner at the Food and
Drug Administration, said 45 million to 52 million doses of vaccine
are expected to be available by mid-October. More vaccine will then be
made available weekly, up to about 195 million doses by year's end.
Q: Where can I get it?
A: The same place you can get seasonal vaccines. Also, some states
will be providing vaccines through schools and health departments.
Contributing: Elizabeth Weise