What is Biology Good For? Keeping Us Healthy During Flu Season: Flu Vaccines
(This assignment is optional and is due on Friday, January 23, 2004 by 11:30 am. 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.)
Every year, the influenza virus causes the death of about 30,000 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. Immune system 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) its DNA rapidly, and each year, many new strains of influenza develop that look 'new' to our body's immune system. Two main proteins, hemagglutnin (H) and neuraminidase (N) , 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. Each flu season usually includes a combination of 'old' and 'new' viral strains. This year, the 2003-2004 vaccine program included protection against the currently circulating Panama A (H1 N2), A(H1 N1), A(H3 N2), and B viruses.
How is the Flu Vaccine made? In the U.S., new vaccines start to be mixed in late summer for distribution in October and November. The new flu vaccine made every year includes the virus strains that are the Centers for Disease Control in Atlanta GA, predict will be most common during the coming flu season. The influenza strains chosen are sent to pharmaceutical companies, and injected into millions of chicken eggs, where the viruses replicate in the egg albumin (egg white) over a process of about 2 months. Virus particles isolated from the egg white are then purified, inactivated, and dispensed into vials. [Image of antibodies].
Double Whammy for the 2003-2004 flu season: (1) Do we have enough vaccine and (2) does the vaccine offer as much protection as usual? Typically, 70- 75 million Americans receive flu shots. In 2002, Aventis-Pasteur and other companies together produced 93 million doses of the flu vaccine - a record number!- at a cost of $2 - $3 per vaccine. However, almost 20 million doses went unused last year, a waste of over $50 million!! Therefore, for the 2003-2004 flu season, production was backed down a bit, to 83 million doses of flu vaccine. Normally, this would have been plenty to vaccinate all the people in the world who wanted the flu vaccine! However, this year a new (and potent) variant of influenza cropped up, known as the Fujian strain, that was NOT part of this years vaccine program since the strains used in the vaccine have to be decided months in advance. Fortunately, the CDC has found that while this year's vaccine may be somewhat less effective against the Fujian strain than in the typical Panama strain, this year's vaccine does offer "some cross-protective immunity" against the Fujian strain and does "reduce the severity of disease", since the two main proteins of the Fujian strain A(H3 N2) are very similar to the Panama A(H3 N2) proteins in the current years program. However, the increased media attention, combined with fewer doses than last year, has resulted in a worldwide shortage of the flu vaccine. Worldwide agencies are cooperating to share the remaining doses of flu vaccine, and other alternatives to the flu vaccine have just become available this year (see below). While the CDC reports this week (January 3, 2004) that the flu season seems to be winding down (and hasn't so far been as bad as predicted), there is sometime a resurgence of the flu in February or March. Stay tuned! Alternatives to a flu shot – a flu nasal spray? After a decade of testing and clinical trials with thousands of volunteers, Medimmune, a biotechnology company in Mountain View, CA, received approval in July 2003 from the FDA (Food and Drug Administration) to market FluMist, a weakened flu virus vaccine delivered to the body via a nasal spray! In clinical trials, FluMist provided up to 93% protection against influenza virus (and no needles!). FluMist became available for the first time during this current flu season, in October 2003. While many doctors offices, clinics, and retail pharmacies like WalMart initially decided to wait out the first season of FluMist to see how the first year of use went, many other clinics and pharmacies did offer FluMist, particularly as the national supply of the Flu vaccine dwindled in late December. How do you know whether you have a cold, caused by a bacteria, or the flu, caused by an influenza virus? Grab a box of Kleenex and see the comparison chart here!
What if you already have the flu - is there any medicine available? Most people who really persisted were able to be immunized this year, and many others are taking precautions to prevent the flu if possible. Antibiotics, of course, are ineffective against viruses. Howeber, anti-viral medication does exist to treat 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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Extra Credit Questions: Please answer all 3 questions in one text box! Note: Clicking the link will open a NEW window so you won't lose your answers! Just close the window to get back to the Good For! 1. List 2 famous flu epidemics, and the approximate number of deaths from each. (See the section "Pandemics"). 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 message that states "You have completed the most recent Warm Up" (even though it is a "Good For!") - as long as you get that message box, I have received your response!