Flu Shot 101: Answering the Important Questions

The first rounds of flu shots are now being administered, but some Americans, even those who’ve read up on the basics of the flu still have questions about both the seasonal and swine flu shots.

For instance, how effective are they? Who develops them? How can the vaccine I get be different from what other people might get? And what kind of side effects might I experience? Here are some answers.

1. If vaccines are made based on guesses of what influenza strains will be around each flu season, how effective can they really be?

If results from decades past are any indication, flu vaccines have been effective.

“Past studies have shown in years when the vaccine viruses and circulating viruses are well-matched, the vaccine can reduce the chances of getting the flu by 70% to 90% in healthy adults,” the CDC says.

“If match is very suboptimal then effectiveness in preventing illness among healthy persons would typically be more like 40% to 50%,” says CDC spokesman Anthony Fiore.  While the CDC wouldn’t say how often strain selection wasn’t so good, “we think there is a good match in most years over past 20,” Fiore noted. If you’re one of those people who have gotten a flu shot and then the flu in the same year, that statement probably offers little comfort.

Effectiveness can also differ for the very young and the elderly, who may be more susceptible to illness, but they can still prevent major complications and death.  “The seasonal flu shot is 30% to 70% effective in preventing hospitalizations due to lung infections in people with chronic conditions like asthma or heart disease, notes the CDC.  And in nursing home residents, the vaccine might be “50% to 60% effective in preventing hospitalization or pneumonia, and 80% effective in preventing death from the flu,” the agency says.

It’s also important to note, however, that the flu vaccine can’t prevent colds and other illnesses with similar symptoms, and it won’t protect you from the flu virus if it’s already in your body because it takes about two weeks for the shots to work, according to the CDC.

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