The FluMist vaccine is administered as a nasal spray to individuals between the ages of 2 and 49. The dosage depends on whether the individual has received a previous influenza vaccine or not.
What is FluMist
FluMist is a nasally administered influenza vaccine. The vaccine contains live influenza viruses that have been modified to no longer replicate in the lungs or be infectious. The regular seasonal FluMist contains three different attenuated viruses. The viruses in the FluMist are expected to produce an immune response in the vaccinated population against the season’s most probable flu viruses. The H1N1 FluMist only contains the attenuated H1N1 virus.
Viruses in FluMist are Cold Adapted
This means that viruses in the nasal spray have been modified and are able to replicate at 25 °F. Most “regular” or wild-type viruses cannot replicate at this temperature. Viruses need to replicate to be able to survive, reproduce and start an infection. The temperature in the nose is ideal for the cold adapted viruses within the vaccine to reproduce. Temperatures in the nose are colder than normal body temperatures. Replication of the virus is important for the vaccine to elicit an immune response in the person receiving the vaccine.
FluMist Has Viruses that are Temperature Sensitive
The viruses within the FluMist have been developed to be sensitive to temperatures. The virus cannot replicate at the temperatures which wild-type viruses replicate. An active influenza virus' wild-type replicates at the normal body temperature of 37 °F. These are the temperatures found in the lungs where the viruses infect. As a preventative modification to temperature sensitive creates viruses within the vaccine will not replicate in the lungs.
Influenza Viruses are Attenuated
FluMist contains viruses that have been attenuated, where the disease causing portion of the virus has been removed. This means that these modified viruses are unable to cause the symptoms associated with an influenza infection. The virus is unable to cause an infection.
How Does FluMist Work
FluMist is administered into nose via the nostrils. The viruses contained within the vaccine infect the cells lining the nose and start replicating. This infection is important in eliciting an immune response. Since the viruses are attenuated the infection does not produce any symptoms. The body creates antibodies in response to the replicating viruses.
How Is FluMist Made
FluMist is manufactured the same way all other flu vaccines are manufactured; in chicken eggs. The modified viruses are placed within sterile chicken eggs and incubated; this allows the viruses to replicate. The fluid containing the viruses in the eggs is then harvested, pooled, concentrated and sterilized before it is packaged into the individual sprayers.
There is no difference in the manufacturing of the FluMist for the normal flu season and the H1N1 FluMist. The only difference is the type of attenuated viruses that are contained within the vaccine.
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