Medical Health Encyclopedia

Timing and Effectiveness of the Vaccine. Ideally, appropriate candidates should be vaccinated every October or November. However, it may take longer for a full supply of the vaccine to reach certain locations. In such cases, the high-risk groups should be served first.

Antibodies to the influenza virus usually develop within 2 weeks of vaccination, and immunity peaks within 4 to 6 weeks, then gradually wanes.

• Because children under age 9 do not develop strong immune responses to one dose, the CDC recommends two vaccinations given 1 month apart.
• Early research also suggests that it may be equally effective to administer children’s vaccinations in the spring and fall, rather than one month apart; further study is ongoing.
• It should be noted that if an individual develops influenza symptoms and is accurately diagnosed in time, vaccination of the other members of the household within 36 – 48 hours affords effective protection to those individuals, according to a 2004 Canadian analysis of multiple studies.

In healthy adults, immunization typically reduces the chance of illness by about 70 - 90%. The current flu vaccines may be slightly less effective in certain patients, such as the elderly and those with certain chronic diseases. Even in people with a weaker response, however, the vaccine is usually protective against serious flu complications, particularly pneumonia. In fact, among the elderly, interesting studies are now suggesting that influenza vaccination may help protect against stroke, adverse heart events, and death from all causes.

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Children Who Should Be Vaccinated. The following children over 6 months should be vaccinated against influenza:

• The American Academy of Pediatrics (AAP) and the CDC recommend influenza vaccination in all healthy children between 6 and 2 years of age. In addition, any child over the age of 2 years with a condition that requires regular medical care or who has been hospitalized for a serious illness (particularly lung or kidney disease, diabetes, sickle-cell, or immune deficiencies). If parents are concerned about vaccines that contain the mercury preservative thimerosal, they can ask their doctor about reduced-thimerosal flu vaccine.
• Children who are receiving long-term aspirin therapy should also be immunized against the flu because they are at higher risk for Reye's syndrome, a life-threatening disease, if they get the flu.
• Some experts now advocate flu shots for all school-age children. Emerging research indicates that children are responsible for transmitting the vast majority of cases of seasonal flu, and that routine vaccination of school-age children would considerably reduce transmission rates throughout communities.