According to the Center for Disease Control (CDC) there are three differents types of influenza virus. They are A, B and C. There are also two types of the A virus; bird and swine flu virus. The C type virus will not cause a pandemic and therefore there is not a vacine to protect against it.
The CDC, the World Health Organization (WHO) and the Food and Drug Administration (USFDA) research the different samples of the viruses around the world and decides which viruses will likely occur again. From there, it is up to each country to decide what they will include in their yearly vaccine. In the United States, the FDA decides this. Having the same vaccine two seasons in a row is unusual but not uncommon. This has happenend eight times, actually, since 1969. For the season of 2011 to 2012 the influenza vaccine will contain the same virus protection as the season for 2010 to 2011. This does not mean we will receive "left over vaccine" from the same batch as last season. Just as we lose a little bit of immunity year by year the vaccine itself has a short shelf life. The expiration date is usually anywhere between March to May of the season for which it is being used.
Research to determine what viruses are prevalent during the year is done in over 106 countries with 136 different laboratories compiling the research. From there each CDC in every country continues the study. Finally, the vaccine is made, distributed and administered beginning as early as September of every year.


Comments
barbarabSep 3, 2011
ohcarolineSep 3, 2011
barbarabSep 3, 2011
Holistic_HealthSep 3, 2011