When a different strain of the influenza virus becomes virulent, it is usually the result of a mutation. Each year before the flu season, it is the Global Influenza Surveillance Network’s task to determine which strain will be used to compose that year’s vaccine. There is a science behind the choice but it is also an educated guess. The Network needs to make a choice early in year prior to the flu season as the process for making the vaccine is lengthy. It takes at least 6 months to produce enough stock to vaccinate the population. In the case of the unpredicted swine flu virus it will take a few months before the swine flu vaccine is available.
Manufacturing Influenza Virus Vaccine Uses Chickens and Eggs
Manufacturing viruses to meet the demands of a pandemic is a challenge. Current flu vaccine manufacturing techniques requires the replication of the virus in chicken eggs. This is a lengthy and time-consuming process. It is important that the Network needs to be certain that they are manufacturing the vaccine against the right strain of the influenza virus. Using the possibility of a pandemic caused by the swine flu virus, it will take some time for researchers to determine which swine strain is circulating, and to also determine if there is only one strain.
How the Influenza Vaccine is Manufactured
Viruses require a host cell to grow or replicate. Using live laboratory animals to grow the influenza vaccine is a costly method. It also raises ethical issues. Since the 1930s scientists have used fertilized chicken eggs to grow viruses. The fertilized eggs are considered relatively inexpensive and are readily available. First a hole is drilled into the egg shell and the virus is injected into a preselected section of the egg; in the case of the influenza virus, the virus is injected into the chicken egg’s amniotic cavity. The amniotic cavity is able to provide sterile and nutrient rich environment for the influenza virus to replicate. The viruses in the vaccine are then recovered by removing the amniotic fluid from the egg. Viruses can also be grown in cell cultures. The cells are cultured in a sterile nutrient rich environment. This method is however limited by the amount of cell culture available for virus growth.
The Future of Influenza Vaccinations
With the possibility of pandemics being inevitable researchers are hoping to develop vaccines that are universal. The universal flu vaccines will have the ability to boost the body’s immune system when faced with any type or strain of influenza virus. These vaccines will not rely on the surface protein of the virus as the base of the immune response but on other biomarkers. The proposed biomarkers include viral proteins, the viruses actual RNA found within the virus and the stem that holds the surface protein in place. These vaccines will immunize against different influenza viruses, bypassing the vaccine manufacturing waiting period.
