Defend yourself against the flu

By Bjorn Carey

updated 2:25 p.m. ET Nov. 22, 2005

You are probably familiar with the nasty and long-lasting symptoms of the flu: runny nose, dry cough, extreme fatigue, high fever and vomiting.

But you might know less about how to prevent infection and treat symptoms if you do become sick. This year, with the world facing the prospect of a pandemic from a bird flu that is spreading around the globe, knowing what to do is more important than ever.

In Part 2 of a three-part series, LiveScience looks at what you can do to protect yourself and those around you.

Do you need a vaccination?
Vaccines contain the virus in an amount or state that will not cause illness but that is enough for the immune system to recognize it as foreign and destroy it.

The immune system also remembers how to destroy the virus so that if you are ever infected by the real thing, your body can quickly set to work neutralizing the virus before it infects cells or destroys infected cells.

Several major diseases — chicken pox, smallpox, polio, measles, mumps and rubella — have effective vaccines that only need to be administered once or twice a lifetime to provide protection.

But influenza is constantly changing, so yearly updates are necessary.

To ensure preparedness for high-risk individuals, this year the Center for Disease Control and Prevention, or CDC, suggested that prior to Oct. 24 vaccinations be given only to certain groups: people aged 65 years or older, those with chronic health, heart, or lung conditions, pregnant women, health care providers, and children 6 to 23 months old.

The CDC suggests that everyone else older than 50 now be vaccinated. The agency does not recommend vaccinations for other healthy individuals but says almost anyone who wants to reduce the chance of contracting the flu can be vaccinated.

However, some people should not be vaccinated, including those with severe allergies to chicken eggs, anyone who have had severe reactions to past vaccinations, and children younger than 6 months. People with moderate or severe illness with fever should wait until their symptoms lessen to be vaccinated.

The front lines
The first line of defense against the flu is constant surveillance of the various strains of the virus, conducted worldwide by the World Health Organization and stateside by the CDC. This system monitors the circulating flu viruses, searching for changes that could lead to new strains.

“If a novel strain emerges, or a laboratory or doctor sees a patient, and tests suggest they have a unique strain, then a sample is sent to the one of the WHO collaborating centers for flu surveillance to determine how novel it is,” explained CDC spokeswoman Jennifer Morcone.

INTERACTIVE Building a vaccine Preparing for the flu, every year

Each January the Food and Drug Administration's Vaccines and Related Biological Products Advisory Committee reviews worldwide surveillance data and makes an initial recommendation about at least one of the three strains to be included in the vaccine. By mid-February, WHO officials make additional recommendations. In March, the FDA's committee meets to finalize the U.S. vaccine.

(A similar process for the Southern Hemisphere wraps up in September.)

The vaccine viruses are grown inside chicken eggs in labs, so as this process is going on, the four licensed manufacturers in the United States begin buying enough eggs to produce 80 million or more doses of the vaccine. Once the vaccine contents have been decided on, the FDA prepares the specific viral material and sends it to each manufacturer to begin production.

Shot or spray
The flu vaccine can be administered as a shot or, for those with a fear of needles, as a nasal spray. The shot contains killed strains of the virus, which doesn't make you sick but still allows the immune system to build a resistance against the surface markers.

Anyone 6 months or older is eligible for the flu shot. The nasal spray, however, is approved only for use in healthy people ages 5 to 49. It contains live, but weakened, flu viruses that do not cause illness, sometimes called LAIV for “live attenuated influenza vaccine.”

This year's flu vaccine protects against Type A subtypes H1N1, H3N2, and Type B Shanghai, according to the CDC. Since the immune system develops recognition of the H1 and N2 surface proteins, this year's vaccine also protects against H1N2, the third Type A subtype commonly circulating in the population.

The avian flu has not yet made the transformation to a version that can spread from human to human, so scientists do not know exactly what type of vaccine should be made to protect against it. If such a strain does emerge, it could take between six months and a year to produce and distribute a vaccine, the CDC's Morcone said. She added that researchers are working to replace the archaic method of egg-based vaccine development with a quicker cell culture-based technique.

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