Influenza vaccine

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Influenza

Influenza vaccines

Overview

Prevention

Definition

An influenza vaccine protects people against the flu.

Alternative Names

Vaccine - influenza; Immunization - influenza; Flu shot; Flu vaccine

Information

The flu is a contagious respiratory disease caused by an influenza virus. In the U.S., flu outbreaks typically occur in winter months. Symptoms include fever, chills, sore muscles, and cough. Thousands of people in the U.S. die each year from the flu or its complications. Most of those who die are the elderly, young children, or people with compromised immune systems.

See also: Flu

The viruses that typically cause the flu are primarily categorized as influenza type A or type B. Influenza type B does not change much over time, but type A can mutate rapidly. Therefore, a new form of the flu vaccine must be developed each year to protect people against the exact strains that are expected to be most prevalent.

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The flu vaccine that will be given during the fall and winter of 2010 - 2011 will also protect everyone against swine (H1N1) flu. There is no separate vaccine for swine flu.

There are two types of flu vaccines: a flu shot and a nasal spray-type vaccine.

The flu shot contains killed (inactive) viruses, so it is not possible to get the flu from this type of vaccine. However, some people do get a low-grade fever for a day or two after the shot as their immune systems gear up to recognize the virus. The flu shot is approved for people age 6 months and older.

A nasal spray-type flu vaccine called FluMist uses a live, weakened virus instead of a dead one like the flu shot. It is approved for healthy people aged 2 to 49 who are not pregnant. The vaccine helps the lining of the nose fight off actual viral infections. It should not be used in those who have asthma or children under age 5 who have repeated wheezing episodes.

Flu vaccines are generally given at the beginning of the "flu season" -- usually late October or early November in the U.S. However, they may be given as late as March, and still provide some benefit.

People traveling to other countries should be aware that the flu may occur at different times.