What is Biology Good For? Keeping Us Healthy During Flu Season: Flu Vaccines
(This assignment is optional. Read this essay and answer the questions at the bottom for 3 extra credit points. It is not necessary to visit the links in the text unless you are interested in more information.)
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Every year, the influenza virus causes the death of about 20,000 Americans and over 1 million people worldwide! People get the flu when the virus enters their body on a water droplet (perhaps from someone nearby sneezing) and invades their cells. A healthy immune system can kill the virus, but the whole process takes about a week. However, the virus replicates so rapidly that a person (especially with a weakened or developing immune system) may die or suffer complications such as pneumonia from the virus before the body can inactivate it. [Image: Los Alamos National Labs]
One way to prevent the flu is by getting a flu shot, or vaccine. Vaccination provides a 'training exercise' for the immune system. The weakened virus injected during a flu shot is carried to the lymph nodes, where the immune system kicks in. B-cells (with some assistance from Helper T-cells) turn on genes to produce antibodies to the virus. These antibodies coat the flu virus and signal it to be digested by macrophage cells in the immune system. If a person then inhales a live virus, the body is already prepared with antibodies to fight off that virus.
The flu vaccine is 70 - 90% effective in preventing the flu, but is good for that year only.The influenza virus mutates (changes) rapidly, and each year, many new strains of influenda develop. Two main proteins, hemagglutnin and neuraminidase, are changed every year as a result of these genetic mutations. That is why a new flu vaccine must be prepared every year, and why people get a flu shot every year.
In the U.S., new vaccines start to be mixed every October and November. The Centers for Disease Control in Atlanta, GA determined that the 2000-2001 flu shot would contain 3 flu strains: A/Panama, A/New Caladonia, and B/Yamanashi. The strains are sent to pharmaceutical companies, and injected into millions of chicken eggs, where the viruses replicate in the egg albumin (white). Virus particles isolated from the egg white are then purified,inactivated, and dispensed into vials. [Image of antibodies]
In November 2000, Aventis-Pasteur, Wyeth-Ayerst, and Medeva together produced almost 100 million doses of the flu vaccine, at a cost of $2 - $3 per vaccine. However, the slow growth of viral strain A/Panama caused the shipment of the flu vaccine to be delayed. People were strongly urged to wait to receive their flu shots, giving priority to children, the elderly, and persons with comprimised immune systems. By December, the flu shot was readily available.
Alternatives to Flu shots: Aviron, a biotechnology company in Mountain View, CA, has just completed clinical trials on a flu vaccine that is delivered as a nasal spray. Once it receives clearance from the Food and Drug Administration, this nasal spray should be available, possibly for the 2001 - 2002 flu season. [Image]
What if you already have the flu? Tamiflu, developed by Hoffman-LaRoche, lessens flu symptoms in adults and may even prevent a person from getting the flu.
Information, images, and quotes from this Good For, and more information on this topic can be found in the February 2001 issue of Scientific American, p. 82-83
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Questions: 3 points extra credit. Click on the links for more information! One sentence should be enough to answer each question . Once you hit 'submit', you will receive a Thank You confirmation page.
Please type your Student ID Number: LAST name: FIRST Name: 1. List 2 famous flu epidemics, and the approximate number of deaths from each. (See the section "Natural History of Human Influenza"). 2. Why do you think a nasal spray would be a good way to deliver a flu vaccine? 3. How does Tamiflu work ? (ie: what are you taking when you take this medicine?)
You may change your mind as often as you wish. When you are satisfied with your responses click the SUBMIT button. You will receive a "THANK YOU" page as a confirmation that your response has been sent to me. *****************************************************************