Flu is a respiratory infection that develops primarily in the lungs and spreads from person to person following secretions of the nose and lungs, especially while sneezing. In medical terms, this viral infection is called influenza.

The common symptoms of influenza include higher fever, more malaise and severe body aches and the viruses are categorized in three types: A, B, and C. While A and B-type influenza are responsible for epidemics of respiratory illness that occur almost every winter, C category usually causes either a very mild respiratory illness or no symptoms at all. Types A and B cause epidemics and can have severe impact on public-health.

In the US, more than 200,000 people are hospitalized following influenza every year and about 36,000 die due to related complications.

The influenza virus can alter itself a bit each year, thus rendering the vaccine used over the earlier years ineffective. As such, a new vaccine has to be prepared with a hope it will be effective against the expected type of influenza virus.

Federal health agency officials each year try to assume which three flu strains are most likely to be prevalent in the US the following year to determine which strains will be included in next year’s flu vaccine. The main points to be kept in mind are:

• It takes about two weeks for the flu vaccine to build protection in your body

• The flu vaccine does not cause the flu

• No vaccine protects 100% from disease. There is a chance you may become ill with the flu even after you get the vaccine

• The vaccine does not protect against colds or other illnesses that have symptoms similar to influenza

After developing the vaccines, officials and various health agencies embark upon the annual exercise of spreading awareness about the need for vaccination and encouraging more and more people to get flu shots.