Viral Influenza Vaccines

Effectiveness and Benefits

Vaccinations now protect against influenza in between 70% and 100% of healthy adults when the virus and the vaccine are well matched. In the absence of a match and among the elderly and children, they are fully protective in 30% to 60% of people.

Annual Redesign

Vaccines must be redesigned every year to match the current strain. The antigens in these influenza viruses undergo genetic alterations (called antigenic drift) over time, so they are likely to become resistant to a vaccine that worked in the previous year. Vaccines are then redesigned annually to match the current strain.

The current flu vaccines may be slightly less effective in the elderly, the very young, and patients with certain chronic diseases than in healthy young adults.

People of any age who are at high risk for serious complications from influenza should be vaccinated. Such people include those with heart disease, lung problems, immune deficiencies, diabetes, kidney disease, or chronic blood disease.

Studies now suggest that the vaccine is generally safe in patients such as those with HIV or asthma, and their risk for serious complications from influenza outweighs any potential adverse effects from the vaccines.

In 2002 the American Academy of Pediatrics (AAP) and the CDC recommended the vaccination for all healthy children under two years of age. This recommendation may vary from year to year depending on the supply of the 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.

In an interesting study in Japan it was found that vaccinating children actually helps protect the elderly.

Allergic Reaction

Newer vaccines contain very little egg protein, but an allergic reaction still may occur in people with strong allergies to eggs.

Soreness at the Injection Site. Almost a third of people who receive the influenza vaccine develop redness or soreness at the injection site for one or two days.