Pediatrician’s Perspective: Flu Shots - What they can and can’t do for you

While just about anyone will benefit from a flu shot, those at highest risk—children less than 5 years old, the elderly, and those with many common chronic health conditions (for example, asthma, heart problems, diabetes)—should definitely be immunized.

The very best way to protect yourself from the flu is to get a Flu Shot.
Like most immunizations, flu shots work on the principle that if your body meets a part of a disease organism—a piece of a virus or bacteria that is itself altered so that it can’t cause disease—then your body can get started on the process of responding, by making antibodies, the little biochemical agents that are an important part of our immune response. Then when the real thing comes along, your body already has custom-made warriors to combat that disease. The process of making antibodies is a long and complicated one that takes weeks to accomplish.

But flu shots cannot guarantee that you won’t get the flu.
Seeing the Future
Creating the right flu shot, the right mix of virus pieces for any year’s flu shot, requires a crystal ball. We need to figure out which types of flu are going to come to our country in the next year. But since we can’t see into the future, we turn to epidemiologists and experts in infectious diseases to tell us what strains of influenza are most likely to affect us each year. Sometimes their predictions are good, but sometimes they are not. Sometimes an unanticipated strain makes it to our shores, and then we have more widespread flu outbreaks.

Individual response to the vaccine
And no immunization is 100 % effective. If you give 100 normal people one flu shot in a given year, between 10 and 40 of them will not respond and they will not be protected.
People who have a suboptimal response to the flu shot might get a milder case than they would have had they not gotten a flu shot at all. Children under age two still have immature immune systems, and may not be able to make as good an immune response as older people. And elderly people may lose their immunity faster than younger ones.

Immune response takes time
Even if you are going to respond to the flu shot in the desired way, it takes about 2 weeks to achieve immunity. But every additional day your body is able to work on its immune response to the virus pieces in the shot probably gives some benefits when you are exposed to the flu itself.

Herd immunity
Children under 6 months of age cannot receive flu shots, some people do not have an adequate immune response to the flu shot, and some people don’t get the flu shot. But all may not be lost. If enough people around them get flu shots, the unvaccinated or under-vaccinated are less likely to be exposed to the flu, and so are less likely to get infected. And for a disease to spread, it has to find another person to spread to before it has been recovered from by the initial victim. If there are only a few or only widely scattered people who can get the flu, the flu will have a hard time finding new hosts, and may die out. These factors contribute to “herd immunity.” This concept explains why we vaccinate those who live with or work with babies. And it reminds us why diseases spread better in crowded conditions.

Other ways to protect yourself
Many times in recent years there have been problems getting enough flu shots for the people who need or want them. And many people chose not to get them or can’t afford to get them. Of course, there are other ways to protect yourself, the most obvious (and most effective) being hand washing and the avoidance of crowds. Certain medications can be taken during periods of exposure to prevent getting the flu.

How do you know if you’ve gotten the flu?
The flu is a very significant illness. It usually comes on suddenly—over hours—and you feel like you’ve been hit by a truck. Classic symptoms are fever, headache, red eyes, runny nose, sore throat, cough, and muscle aches.

Ways to treat flu
And if you do get the flu, unless you have some serious underlying health problems, you will probably do fine if you use common sense, take it easy, and remember not to expose others. For children, aspirin-containing products should be avoided, because they can cause severe complications. It’s OK to use acetaminophen or ibuprofen for fever control and comfort. There are quick and easy tests to diagnosis flu, and there are medications that can treat it. These medications have to be started in the 1^st two or three days to be effective, so if you are really suffering, see your doctor quickly.

Margaret Morris, MD
September 25, 2006