Person to Person
The main way that influenza viruses are thought to spread is from person to
person in respiratory droplets of coughs and sneezes. (This is called "droplet
spread.") This can happen when droplets from a cough or sneeze of an infected
person are propelled through the air and deposited on the mouth or nose of
people nearby. Influenza viruses may also be spread when a person touches
respiratory droplets on another person or an object and then touches their own
mouth or nose (or...
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Is the 2009 H1N1 swine flu vaccine safe?
No vaccine is 100% safe for everyone. People with allergies to eggs, for example, can't take flu vaccines
because eggs are involved in the manufacturing process.
And flu vaccines cause mild but common reactions. About one in three people
get a sore arm from the shot, some with a little redness or even swelling. Some
10% to 15% of people feel tired or get a headache; some may even run a low fever.
And vaccines can trigger rare but serious reactions, even among people with
no apparent allergies or sensitivities.
So if vaccines aren't 100% safe, why risk them?
Approved vaccines -- including the 2009 H1N1 swine flu vaccine -- are
calculated to be much, much less risky than the diseases they prevent. For
example, out of every million people who get a flu shot, one or two will get a
serious neurological reaction called Guillain-Barre syndrome (GBS).
But flu itself causes serious problems, including GBS, in far more than two
in a million cases. And since a large proportion of the population will get
swine flu, the vaccine risk is far smaller than the disease risk.
In clinical trials, 10,000 to 15,000 children and adults have received
various manufacturers' brands of H1N1 swine flu vaccine. Nothing serious
happened to any of them, including this reporter, who received a double dose of
the Sanofi-Pasteur swine flu vaccine.
That's still not proof that no harm will come from the vaccine. Clinical
trials cannot detect something bad that happens to one or two out of every
100,000 people vaccinated.
"There could be unknown side effects. Something could happen. But we think
that is highly unlikely," says infectious disease and vaccine expert Mark
Mulligan, MD, executive director of the Hope Clinic of the Emory Vaccine Center
"The CDC, FDA, HHS [Health and Human Services Department], the Department of
Defense, and several large HMOs with great medical records are all
collaborating in enhanced surveillance for this national 2009 H1N1 vaccine
campaign," Mulligan tells WebMD. "If there is a signal for a rare or late
adverse event, we will identify it as early and as quickly as we can."