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Why There is a New Flu Vaccine Every Year

Cooler temperatures, leaves changing colors, and signs for flu shots everywhere. It must be autumn.

Just like pumpkin spice, the annual flu shot has exploded in popularity in recent years, increasing from about 12 million doses administered in 1980-81 to over 155 million last year. This is great news for everyone looking to stay healthy and protect the people around them.

Whether you choose to get your flu shot at a doctor's office like Nu Wave Medical Center where Dr. Gurprit Sekhon and her staff administer vaccinations as part of their full-service internal medicine practice, at a local pharmacy, or during a vaccination clinic, it's now easier than ever to stay up-to-date on this important immunization.

But why is it necessary to re-vaccinate every year?

How vaccines work

Vaccines perform by injecting killed or modified versions of viruses and bacteria called pathogens into the body to create an immune response. Since the pathogen is inactivated, you will not actually get sick, but your body will recognize the intrusion and create specialized antibodies against the particular disease. The antibodies remain at the ready until you're exposed to the real pathogen at which point they attack and neutralize it before you become ill.

Why flu shots change

Many diseases like pertussis, measles, hepatitis, and others stay the same, so as long as you're properly vaccinated, it doesn't matter if you're exposed the next month or years later, the antibodies are still ready to demolish the intruder and keep you healthy. The problem with the flu virus is that it's always changing so that it can survive.

The flu pathogen replicates by invading a cell, turning off its antiviral response, and then making copies. If you have gotten a flu shot that matches the virus (or have previously been infected with it), the antibodies you have already generated attack and prevent more cells from being hijacked, thus preventing illness. This is bad news for the flu virus.

To try to get around this, flu viruses change slightly, so the antibodies can't recognize and neutralize them. To encourage these mutations, replication occurs very fast, with new viruses being released from cells in only six hours.

Unfortunately, the section of the virus that changes is also the part that vaccines target, so after a mutation, the immunization becomes ineffective. Thus, vaccinations need to evolve along with the virus to keep working.

Also, over time, antibody levels can decrease and make the immunization less effective.

How flu shots are determined

Creating each year's flu shot takes careful research and analyzing of data to develop what researchers believe will be the best possible match. Throughout the year, more than 140 influenza centers located in more than 100 countries compile data on which strains are affecting people in their areas, how well the viruses are spreading, and how effective earlier vaccines were against them.

This information is then passed on to five World Health Organization influenza research centers in the United States, United Kingdom, Australia, Japan, and China. Scientists from each location gather annually in February to determine which strains will be included in the northern hemisphere flu vaccine and again in September to decide which will be in the southern hemisphere version. Manufacturers then have about six months to make the vaccine.

Researchers are working on finding a new approach to a flu vaccine that could last longer and cover a wider range of strains. Until then, getting the annual recommended immunization is the best way to try to avoid the flu. Call or click to book an appointment with Dr. Sekhon today.

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