A major advance in the ability to fight off infections due to influenza viruses, or numerous other diseases, was the development of vaccines. Being immunized against any influenza virus dramatically increases the ability of the body to prevent getting the infection. Over the last several years, vaccine research has provided an alternative immunization method to the standard injectable flu shot, a nasal spray based vaccine. How are they different and how does this effect the choice of using one over the other?
The Flu Shot
Every year, the population faces what is known as the seasonal influenza. This year, the stakes have been raised because of the emergence of the so-called Type A H1N1 2009 influenza, or swine flu 2009. For many years, immunization against influenza has been undertaken using flu shots, where the person receives an intramuscular injection, usually in the upper arm muscles. The flu shot contains a suspension of killed influenza virus particles, what is otherwise known as “inactivated virus vaccine.” The immune system reacts to the components found in the killed virus and develops an immune response.
The likelihood of specific seasonal flu viruses changes every year. There are numerous different types of influenza viruses. Influenza specialists around the world watch for and predict what “strains” of flu virus are most likely to be prevalent in a given year and based on those recommendations vaccine production is undertaken. This happens every year and these injectable inactivated virus vaccines are made by the same general process.
FluMist® Nasal Spray
Beginning several years ago, a new approach to vaccinating against influenza virus was developed. Instead of the typical injectable inactivated virus vaccine, a nasal spray vaccine delivery system was developed. The nasal spray, also known as FluMist®, does not use an inactivated, or killed, virus preparation, but rather uses what is known as “live, attenuated virus.” In this case, the influenza virus particles are grown in production laboratories in such a way that they become much less virulent; that is, they have been dramatically weakened and generally do not cause severe, problematic symptoms. This attenuation process allows them to still be active, to still look like the virus trying to be defended against and to still cause an immune response in the person getting the vaccine.
When the nasal spray vaccine is used, the weakened influenza viruses can and do replicate themselves, which leads to the body developing an immune response. These preparations can cause mild illness, but generally do not cause the severe influenza against which they are meant to provide protection.
Vaccine by Shot or by Spray
Because of the differences in the way that these two types of flu vaccine work, there are very important differences as to who should or should not get a specific type of vaccine. The nasal spray vaccine is only approved to be given to people between 2 and 49 years of age. And within this age range, it is not recommended to be given to anyone with a suppressed immune system, pregnant women, people suffering from long-term chronic health problems including heart disease, lung problems such as asthma, kidney or liver disease, diabetes and several others.
The only way to be certain about which type of vaccine is right for you is to speak with your healthcare provider about any and all vaccines before having them administered.
For more information about flu vaccines visit the US Centers for Disease Control Flu pages.
Read the specific approved indications, uses and administration requirements for FluMist listed by the US Food and Drug Administration.
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