According to the Centers for Disease Control (CDC), the new H1N1 flu vaccine (the live, attenuated virus) should be available by the first week of October. There are currently 2 types of vaccine available:

• live, attenuated vaccine (approved for people between 2 and 49 years of age who are  not pregnant and do not have chronic health conditions) that is administerd by nasal spray
• inactivated virus (dead virus) that is administered by injection

The live, attenuated (weakened) virus has been treated in such a way that the virus cannot replicate in body temperatures of 38 or 39 degrees Centigrade (above 100.4 F), which is the temperature in the lower airways and lungs. The virus however can replicate in the cooler temperatures found in the nasal passages.

In this way, the body is able to produce an immune response to the weakened virus that is sprayed into the nasal passages. Because it can’t go on to replicate in the lungs, there are no serious side effects ( ie, pneumonia).

People report mild flu-like symptoms from the nasal spray.

The second type of vaccine is administered by injection and this virus is dead, so it cannot replicate in the body. The immune system however recognizes the virus as foreign and remembers the virus in the future so that if you come in contact with that particular virus, your body is able to defend itself.

For more information, the Advisory Committee on Immunization Practices (ACIP) offers a wealth of information about all immunizations available in the U.S.

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