For starters let us look at what is the flu shot first.

The standard flu vaccine (or, the “flu shot”) is made from flu viruses that have been grown on fertilized chicken eggs. The viruses are killed during manufacturing, a process known as “inactivation.” These inactivated viruses are a source of proteins or antigens that trigger a protective antibody response when the vaccine is injected into the arm or thigh muscle. Antibodies against flu viruses begin to appear one to two weeks after getting the flu shot and last for months, and sometimes even up to one year.

The standard flu shot is the main flu vaccine that will be offered at PAMF for the 2015-2016 season.

Three other flu vaccines will also be available to certain patients:

1) FluMist nasal spray vaccine:
FluMist, an intranasal vaccine, is available to patients 2-49 years of age who have no contraindications to it.

2) Fluzone High-Dose:
Fluzone High-Dose vaccine, a flu shot with four times the antigen dose per strain as standard flu vaccine, is approved only for persons 65 years of age or older.

3) Flublok:
Flublok is a recombinant flu vaccine manufactured without the use of eggs. It is indicated for highly egg-allergic persons aged 18 years or older. It is available only in our allergy departments.

PAMF has transitioned from trivalent to quadrivalent flu vaccines (containing 2 A strains and 2 B strains) with the exception of Fluzone High-Dose and Flublok which are still trivalent (2 A strains and 1 B strain). The second B strain was added to quadrivalent vaccines by manufacturers because predicting which flu B strain would circulate in any given season proved difficult. While this is a modest change, scientists hope it will result in increased protection against the flu in coming years. The higher dose of antigen in Fluzone High-Dose vaccine produces higher antibody levels in patients 65 years or older which results in a modest boost in effectiveness compared to the standard-dose vaccine.

Because vaccine strains often change from one year to the next and immunity wanes, flu vaccine must be given every year. In more depth of explaining this is as follows:

Like stated the influenza viruses are constantly changing. They can change in two different ways.

One way they change is called “antigenic drift.” These are small changes in the genes of influenza viruses that happen continually over time as the virus replicates. These small genetic changes usually produce viruses that are pretty closely related to one another, which can be illustrated by their location close together on a phylogenetic tree. Viruses that are closely related to each other usually share the same antigenic properties and an immune system exposed to an similar virus will usually recognize it and respond. (This is sometimes called cross-protection.)

But these small genetic changes can accumulate over time and result in viruses that are antigenically different (further away on the phylogenetic tree). When this happens, the body’s immune system may not recognize those viruses.

This process works as follows: a person infected with a particular flu virus develops antibody against that virus. As antigenic changes accumulate, the antibodies created against the older viruses no longer recognize the “newer” virus, and the person can get sick again. Genetic changes that result in a virus with different antigenic properties is the main reason why people can get the flu more than one time. This is also why the flu vaccine composition must be reviewed each year, and updated as needed to keep up with evolving viruses.

The other type of change is called “antigenic shift.” Antigenic shift is an abrupt, major change in the influenza A viruses, resulting in new hemagglutinin and/or new hemagglutinin and neuraminidase proteins in influenza viruses that infect humans. Shift results in a new influenza A subtype or a virus with a hemagglutinin or a hemagglutinin and neuraminidase combination that has emerged from an animal population that is so different from the same subtype in humans that most people do not have immunity to the new (e.g. novel) virus. Such a “shift” occurred in the spring of 2009, when an H1N1 virus with a new combination of genes emerged to infect people and quickly spread, causing a pandemic. When shift happens, most people have little or no protection against the new virus.

While influenza viruses are changing by antigenic drift all the time, antigenic shift happens only occasionally. Type A viruses undergo both kinds of changes; influenza type B viruses change only by the more gradual process of antigenic drift.

All flu vaccines at PAMF will be Thimerosal-free and latex-free.

Here are a few reasons why you absolutely need to get a flu vaccine this year:

• Influenza (the flu) circulates all over the world, and it can affect anyone, regardless of their age or health.
• The flu can lead to complications like pneumonia, ear infections, and sinus infections. It can also worsen existing conditions, like asthma or diabetes.
• Each year, thousands of people in the U.S. die from the flu and its complications.

So you may want to think twice of avoiding the flu shot personally but most of all having your children avoid the flu shot.