We have to get flu shots every year because the strain of influenza that causes the flu changes every year. Therefore, the flu shot itself has to change.
In 2009, the H1N1 (swine flu) pandemic began and a vaccine was quickly developed to protect people against that particular strain of influenza. However, due to the timing of the outbreak, drug companies were unable to develop the H1N1 vaccine quickly enough to be included in the seasonal flu shot for the 2009-10 flu season. So that meant anyone who wanted protection against the seasonal flu and the H1N1 pandemic flu had to get two different vaccinations.
What is Different This Year?
However, for the 2010-11 flu season, the strain of influenza that caused the H1N1 pandemic will be included in the seasonal flu shot. Three strains of influenza are included in the vaccine each year, and the pandemic H1N1 strain will be one of those strains in the 2010-11 seasonal flu vaccine. This includes both the flu shot and the nasal flu vaccine -- the strains included in these two vaccines are the same every year even though they are manufactured in different ways.
As always, any child under 9 years old that has never received a flu vaccine before will need two doses.
Do I Still Need a Flu Shot if I Got the H1N1 Vaccine Last Year?
Yes! Even if you got the H1N1 vaccine in 2009 or early 2010, you should still get the seasonal flu vaccine for the 2010-11 flu season. It will protect you against other strains of seasonal flu and will provide added protection against H1N1. Typically, flu shots are effective for about six months, so getting another dose of H1N1 in the 2010-11 seasonal flu vaccine can only help protect you.
Sources:
"Protection Against 2009 H1N1 To Be Included in 2010-2011 Seasonal Flu Vaccine." Flu.gov. 22 Feb 10. US Department of Health and Human Services. Accessed 22 Jul 10.
